1. I have played against Rebel beef, Imp Aces, and FO Aces.
2. Setup against most lists is to have C on the outside with 4-LOM in the middle and A right next to him. Keeping all of them withing range 3 of each other for the ADB ability.
4. Having C on the outside allows him to arc dodge and flank on his way in. When you are about to engage you acquire lock ,then have the other two pass a calc token each to him so he has full mods. Using 4-LOM to try and block in the middle, and to also pass stress. A is a support until the opportunity presents itself for him to dish out some damage.
5. With the ADB ability you can decide which ship is the workhorse each turn if you get some solid blocks or arc dodges you simply pass the tokens to the ship with the best chance of inflicting the most damage, when passing stress to ships with 4-LOM it usually sets up good shots on that ship next turn as it makes their move more predictable. I have a easy time punching in damage with every ship but usually i pump an IG with calc tokens and target lock for maximum damage.
For the rest of your questions, I've been playing since day 1 and found mid base ships are my favorite to fly. They arent to small and not too big and clunky like big base ships. In my experience they are the best. they can fit where bug bases cant and get father than small bases. But give it a try and let me know how it goes for you! Hope this helps!