Dr Croubie,

You picked a variety of films and a variety of cameras. One way I organize the variety is to build from strengths of each format. When I shoot 35mm I "require" a higher-quality negative, so I tend to shoot "slower" films. [Notable exception - tkamiya encouraged me to experiment with accentuated grain in Tri-X]. Normally I want detail. So I would keep fresh 100 speed film and 400 speed film on hand.

The corollary, for medium format and up, I take advantage of faster films. I shoot them at lower (EI) Exposure Index. I just keep fresh 400 speed film on hand.

I develop my film and do tests too (be happy to help you learn the ropes as you get into it), one main lesson I've learned is to give enough exposure for the shadows - keeping in mind the speed that I get in my processing. One shortcut to good shadows is to choose an arbitrary lower EI just because other people find it works for them. For example through tests and feedback I found 400 TMAX works well for me rated at EI 250.

I don't know any downside to shooting 400 speed film at 250.