How tight should studs be when framing a wall and cutting them to length and installing them in-place? Ideally I'd be able to cut my wood accurate to 1/64th, but that ain't happening. If they are a little short than the stud will just wobble, but if they are long then they need a little nudge with the hammer. The friction seems to be the way to go, but are there problems if the stud is TOO long? (i.e. can the floor move up, thereby pushing on the studs -> joists? FWIW, I'm on the East Coast and not somewhere crazy like CO where they have to have floating walls.
I assume that you're referring to interior, non-bearing walls, such as those in a previously unfinished basement. Ideally the studs will fit just snugly enough to hold them in place as you nail them in. You're right that you can jack up the floor if you force them in, but it's more likely that they'll bow a bit.
If they're slightly short it will be more challenging to nail them in accurately, but it won't likely cause any issues. Most of their function is to support drywall, and they'll do that just fine. You can always pop a shim in at each joint, or squirt a dab of construction adhesive to fill the gap.
You have 2 different scopes. One is structural the other cosmetic. If the studs are too short, the nails are being asked to carry more than they should. It will eventually compress. If they are too long, you will distort the floors and walls leading to unsightly finished details.