I don't think you can reliably prevent the opponent from getting Warlords, so the second option is not really an option. Until it is clear which way the Warlords split, you should always* build a deck that can handle a Warlord attack. In that sense, I find the article misleading.
Other comments:
- the strong synergistic relationship between Battle Plan and Warlord really wants to be emphasized. Warlord triggers Battle Plan and gives you a larger hand size so next turn it's easier to connect Battle Plans. This often means that even on boards where Warlord's attack isn't relevant, you want both cards.
- Archer's attack gets a lot less impressive once your opponent plays Warlords.
*unless you have access to the real second option: being unaffected by Attacks.
You can prevent the opponent from getting a shot at Warlord if they have only 1 Battle plan to your 2 (or 3) reliable plays. Say we buy out the Battle plans but I get a 3:1 split. During my turn I rotate the pile from Archers, to Warlords, and then rotate again. You can now only rotate to Archer. As long as my engine is reliable enough, I can keep leaving you 2 rotations away from Warlords until you eliminate another card type from the pile. Eating 4 green early or gaining 2 additional "terminal silvers" is harsh on the deck. And obviously this completely fails if you can throne, Outpost, or otherwise play two rotations before I can reassert control. This can make gaining a third plan an absolutely killer strategy, but it is a high-risk, high-reward option.
If you end up with an advantage that is best maximized by burying all four Warlords (e.g. you get something like Huntingrounds/Tools/Lost Arts) you may want to just deny until the end game when buying green makes it hard for the opponent to break your engine regardless.
These are, by far, the minority of games. Most of the time, you cannot get a 3:1 or 2:1 split on the Battle Plans. Even when you can win that split, you need to get reliable or lucky quick to get past Warlords without the opponent getting a chance. And if everything doesn't align, you almost always want to take the first Warlord you can rather than flipping past to deny. You have very high odds of splitting the Warlords and not too shabby of odds of getting a 3:1 split (with some nice options where you get a 2:1 or 1:0 split for a few go rounds).
Archer is weaker when you look at the 7-card setup; it goes from being discard the second "best" card to discard the the 2.5th best card (roughly speaking, the next two draw cards have a 1/5 chance each of being better than your current second best). However, the flip side is that Archer is very strong once the warlords get going if people have only 2 copies of clutch cards in their deck. For instance, suppose we are doing Warlord/Fortress/Procession as our key engine setup with no other source of additional net actions. Archering either a Procession or a Fortress can allow us to make the opponent to draw fewer cards, have fewer actions for what they draw, and give us good odds of disrupting their engine. Which then makes it harder for them to align Battle plans and attacks in just 5 (or 4 .5if we are using cantrips). Even just discarding a second Village can be a world of pain for an action limited deck. And more insidiously, killing a +buy can literally be like getting a free turn. Warlord decks are fragile and one of the biggest skill components is knowing which card to protect/discard off the Archers.
When the clash pile is on the board, you have 2 options:
The first option is to build a deck that functions under the Warlord attack. Even if the pile's not on Warlord yet, putting a 3rd peddler or a 3rd vanillage into your deck is a liability because in the endgame, when your opponent finally picks up a warlord, you'll have unfortunate stop cards. However, if there's strong TFB on the board (Salvager, Apprentice, Expand, Graverobber), then maybe the extra copies of the card aren't so bad. This option, building a deck that functions under the Warlord attack, is really the default, as the other option is convoluted to make happen. However, a deck that functions under the warlord attack does have less potential than one that doesn't need to worry about it.
The second option is to prevent your opponent from getting Warlord. This can be done by gaining all 4 Warlords, by gaining 2 Warlords and rotating the pile off of Warlords before your opponent can gain any, or by trashing the opponent's warlords. This option has higher potential than the other option, but it's much harder to pull off. Having the higher-potential long-term deck is especially good because Territory provides a bit of alt-VP, but you have to judge on each board whether it's worth bothering. Obviously if the stuff for a sneaky rotate or 4-card-gain is the stuff you had in your deck anyway, then yeah go for it, but that's not always the case.
Getting into each card:
Battle Plan has 2 pieces: Sometimes Lab, and rotate a pile. If you're on this forum, you probably know when you want Sometimes Lab. Rotate a pile is a way to control who has Warlords. If you can rotate to warlords, then gain 2 warlords with remodel or altar or something, then rotate to Territories, that can be game-winning. Also look out for tricks with rotating other split piles, like denying your opponent Catapults or Encampments.
Archer is a rather strong attack, a bit stronger than Militia.
Warlord is extra draw in a deck that it's hard to add draw to under the warlord attack. Adding each successive warlord to your deck is kinda different. The first warlord means you're hitting your opponent on half of their turns. Not being able to play a bunch of your action cards on half of your turns is brutal, so the first Warlord is pretty good. The second warlord balances the duration draw and means the opponent is getting hit every turn. Some decks are better at living when hit on half of the turns than others, and if your opponent is playing such a deck, then the second Warlord is important. The third warlord prevents the opponent from getting a second warlord, but doesn't do much else. If you can fruitfully TFB it or you're building a deck that can get hit by Warlord attack half the time, then it can be worth picking up. The fourth warlord prevents the opponent from playing the warlord attack, so you can build freely.
Territory is usually Duchy. You'll know when it's not.
Even if you cannot trash out a third Warlord, the question is, how useful is it to be able to have some turns where you can play everything, and how bad is it, really to put a curse in the deck. Take the obvious example - you can build a megaturn deck with Hop and Teacher or something if you gain a 3rd Warlord you can still cash out that way, your opponent never can (assuming you always ignore the option to play two Warlords when the opponent might Warlord you in response). Additionally, suppose everyone can build equal decks. The third Warlord means that your deck needs +1 net cards of draw to get through it. What happens to your opponent? Well, they end up with net -1 as the Warlord draws +1 card as they go through. In terms of draw in most situations (e.g. obviously not special stuff like Wt) you buying a "curse" is a net wash. But then remember that a non-trivial number of Battle plan draw comes off the odds of hitting attacks (particularly in decks where you have only 3 attacks from Clashes), you actually come out ahead of your opponent for draw once they start missing the +1 draw for not having enough attacks and you start making a few +1 draws for having one additional attack. Obviously, the call to get the 3rd Warlord depends on what else is on offer, but it generally is a stronger from of net draw than most of $4 Lab variants (e.g. Advisor, Wishing Well) and even a few of the $5s (e.g. Hunter).
Territory is very rarely Duchy if you play it down. First while Warlord mitigates against emptying piles, it does happen (e.g. TfB, Moat, cursers) and those golds make it ~a Harem (less draw efficient, more useful for TfB & spiking $8 or whatever). Second, once you grab two Territories, getting an estate is now equivalent to a Duchy. That will let you dance deeper for long endings and will let you break parity (particularly if you can get 3 Territories). Unless gains are exceedingly tight or the game has potential to immediately end in the next 2 turns, Territory is normally better than Duchy. This can become particularly acute when you consider if you should leave the pile on Archers or on Territories. You can win a small percentage of games just because people forget to flip the Territories on their turns. Lastly, a lot of games will leave the pile with 4 Territories and 2 Archers, buying Territories leaves an easier 3-pile (e.g. copious buys, Worm, Wt) if you might be able to flex for a two archers.
Yes, the difference is small, but at high level play among equals these are the sorts of places you can actually find edges.
The other thing I would note is that Clash games play completely different if you can play cards from outside the hand. Prince can completely negate the impact of action starvation (i.e. in most Clash games you play 3 terminals a turn or fewer when there is a single village out; Prince can let you play 12). Golem can be absolutely amazing, particularly with stuff like Tr - you can easily play scads of identical cards from the discard. Vassal, particularly if you can control the discard with something like Marquis or Innkeeper where you can dump 6 Vassals into the discard, can just be nuts for efficiency. Herald is swingy but can enable hit-or-miss megaturns. Obviously, Piazza and Necromancer are both not so great options. Delay, Gamble, or even March can let you generate big turns on a slow board if you can set things up correctly (e.g. Gamble requires trashing, limited draw, and lots of +coin/golds, March/Bridge trolls can let you have two Trolls in play, buy and play more Trolls for just $5 on average or less).