Well, theoretically for Swiss system to work without tie-breaker, you'd need 3 rounds for up to 8 players, 4 rounds for up to 16 players, 5 rounds for up to 32 players, and 6 rounds for up to 64 players. But logistics and venue opening hours kinda clash with those requirements, and weekend-long tournaments are more expensive (if you don't happen to live where it happens).
I would not differentiate max points by round number. I don't see why it's necessarily tougher to win a 4 round tournament. It's maybe a bit more random, because all games a win is not always enough to win the tournament and the first random pairing has a bigger impact. But in the end the top players will place well, and scoring full (-1) points for 2nd place in a 3 round tournament where I would have ended up 1st after a 4th round is still not bad.