I think it's important to consider where in the story the pauses should be and not think so much about how long it is. You can have a longer chapter and a shorter chapter as long as the pacing is done well. :)

For me, a short chaptered story would work because I never have enough time (or, to be terribly honest, the concentration) to read a long oneshot in one go. Still, it's entirely up to you (and I just evened out a and b again sorry haha) it doesn't matter too much because the story will be the same and awesome either way <3

Depends. Some stories gain a lot from some pauses and/or cliffhangers, whilst others (for example more poetic ones if you like to call them that) needs to be read in their entirety. That is my personal opinion :)