I've yet to play 400, but I can't imagine anything above 600 would be as smooth as it is now. 300 gets fuzzy with heavy fighters.
400 (even with everything being new) wasn't that bad. total: 6 ships, 11 squadrons.
I think wave 2 is going to discourage taking lots of small ships, as if you are in range an MC80 or ISD is too. Which means 8 dice incoming (or more), and most small ships melt when confronted by that. We'll see, but when a Glad goes poof in a single ISD forward shot, How do people think lighter ships will do? (A few small ships would be good, but they are going to need to maneuver very carefully. Neb B is actually the most survivable of the small ships, now, IMO. No redirects, but dual brace, so it's hard to knock out. It won't be feeling good, but it won't be dead.)
more small ships = more activations = well, opponent, I guess you gotta move into position for the firing squad. Come on now, don't be shy!