What should I expect after MEPS since I'm re-enlisting as a prior service?

The MOS that is best for post military life is the one you enjoy doing. Most people don't do what they did in the military after they leave, but the leadership skills and education they leave with set them up for success.

How the Cadre at AIT will treat you is really irrelevant. It's not your duty station, it's a school, and each school has their own rules and policies.
As for PT, you'll have to PT like any other Soldier and alongside the other Soldiers. When and where you get your uniforms depends on what happens at the MEPS, and you can ask them when it's time for your orders.
Again, don't fall for the "what's best for after the military" nonsense. If you stay in long enough, the MOSs merge at the senior ranks and you'll be a 35X anyway. Or maybe you'll go to OCS and become an MI officer. Don't miss the forest because you're focused on the trees.

I'm currently in fort Benning reclassing after av4 year break in service. We are in prior service barracks. We are separate from the recruits and treated very differently than them. We have a drill sergeant that oversees us but we mostly handle things on our own.

I had a break in service and came back in, though that was a long time ago. MEPS is like the first time. I was shipped to Ft. Leonard Wood to inprocess and that's where I got my uniforms. You'll likely be on a hold status why they process your clearance. My peers and I had to wait over 6 months! You will probably be assigned to some sort of prior service platoon where you will assimilate back into military life. You should be treated like any regular service personnel not in training. Good luck!