Can you contract with more than one company at a time?

This mainly pertains to OTR, since with local and dedicated you'd presumably be doing the same thing each day.

How long do contracts usually run in case you don't like it and want out? Typically, what are each party's obligations under the contract?

How many companies can you legally or realistically contract with at the same time? The more the merrier? Seems to me, if you end up somewhere empty, the more companies available to you, the greater the chance of getting you out of that city with a load. If there are multiple options, the choices increase, no?

Could you contract with several companies at the same time, review each trip offer, then pick and choose which jobs you want to accept from day to day? If so, how often, or what percentage of the time would you have to accept work before a given company decided you weren't worth having on their books, due to them offering you stuff you weren't going to accept, and then cancel their contract/relationship with you?

Or is it more like - any decent company will keep you so busy, you won't have time for anyone else, just as with their company drivers, so don't even think about more than one?

What is the procedure for establishing a working relationship with a company, then finding out what runs are available? Do they have secret websites that only their drivers under contract can access, listing upcoming jobs, and it's first come first serve, such that you pick and choose what you want to take on and when? Do they even care how often you take a run for them? Or is it more personalized than that, such that they contact drivers directly, one at a time, offering them runs in a particular order, based on where a person is geographically and their likelihood of taking it?

All I know is, I saw a youtube video where a guy contracting with Prime was talking about how drivers will say they don't want to drive east, but then when they see how much more it pays, change their minds. Somehow, somewhere, he found out about a run that paid $2000+ that others didn't seem to want and shouted "I'LL TAKE IT!" but didn't elaborate as to the process. I don't know what he was seeing/hearing to even find out about the run, how it was offered to him or others, or if he was required to ONLY work with Prime. His main point of the video was that he liked how quickly Prime gets direct deposits into his account or on his card that he has.