ok, what does garrisoning troops inside mechs do for you? is it like turrets, and gives the mech more firepower? is it just for transportation? i dont know if im just retarded or what, but i cant figure it out

The latter. It's helpful if you want to conserve troops, especially if your troops get wounded. I find it helpful to carry a few ground troops to take out any forces that get inside the mech's range or bring some anti-air troops to jump out when fighters/bombers/cruisers approach. It's also good for carrying a few workers to repair the mechs or build and a few medics to keep everyone nice and healthy.

Kryllith