"Essentially yes. Having 40 players instead of 32 in a rock-paper-scissors contest is going to produce less 5-0s then having 40 instead of 32 in a dominion tournament."
Care to put some numbers on that? I mean, I think you're right, but I think it's something like 1.26 on average instead of 1.25, and only because in the final round a 4-0 player paired down against a 3-1 player is more likely to have a 55% winrate than a 50% winrate like he would in r/p/s. The difference is really really negligible.
As for what will and won't make top 8 in 5 rounds of swiss, that's easy enough to calculate (on average, since anything other than 32 results in non-clean results). With 40 players and 5 rounds, 7.75 players reach 4-1 or better, on average. With 48 players, 9 players reach 4-1 or better, on average. etcetc