Pages are entirely the wrong granularity. Just about any 5e game that used that to describe amount of house rules (vs. setting changes, which would be fine) would be a huge red flag for me not to join. Since the minimum non-zero is is 1 page "reasonably used/full" there is no poll entry I can truthfully answer.
My 5e house rules:
1. Inspiration is a reroll chosen after seeing the roll, not Advantage
2. Drinking a potion yourself is a bonus action.
Done.
EDIT: I enjoy a bunch of different game systems. 5e is my favorite D&D, but it's not my favorite D&D-like game. But 5e has the advantage of being everywhere. If I am going to play a game that's like 5e but different enough that I need to rememebr differences from the other games I'm in, I'd much rather have a clean break and just play a different game system.