I usually print on 8x10 paper regardless of film format. I also print with fairly wide borders on the paper, normally 1 inch on each side. I'm printing mostly for holding in hand and viewing. Occasionally prints go on the wall. From 6x6 negs I usually print square for a vertical orientation of the paper. If the composition calls for it, I'll crop. Except for contacts from 5x7 or 8x10, a don't normally print out to the frame edges, but try to get close.
I consider 35mm iffy any larger than 8x10, but I have a couple of photos from 35mm enlarged to 8x10, very good lens, tripod and TMax-100 film. They work.
I designed my darkroom to handle up to 16x20, but have never printed bigger than 11x14. I consider big prints too much hassle in storage mostly.