The easiest way to get more FPS, it seems, is to lower the Render Quality slider. I have mine at 75%, and terrain and texture quality turned way down.
Just went and turned them down even more. Good framerate makes such a huge difference in gameplay.
In my experience, the render quality makes the game look like total ass but does almost nothing to improve FPS. I think if you are GPU bottlenecked, render quality will help but for CPU bottleneck (which afaik is most people) it does nothing.
What helped me by a massive amount (my system is actually under the minimum requirements) is turning the draw distance down. The default (for some reason) is massive, far longer then you can actually see. Unfortunately you can't change it ingame
What you do is open useroptions.ini and find the render distance line, it's probably set to -1.00000 (which means unlimited/server controlled or something like that). I turned mine to 300, which is super low (but my computer is terrible) you could probably try 1000 for a start, and go up or down from there depending on how well it runs. More then 3000 is probably a waste, and even as low as 300 is very playable (just don't try to fly because there's too much fog to see other planes or ground targets).
As for MAXs, they are just too expensive to upgrade (and some of the upgrades, like lower damage from infantry weapons, are a joke). Why would anyone spend thousands of certs upgrading a max which dies almost as fast as an infantry but can only be spawned every 10(?) minutes? They just cost too much for what you get.
Best AA right now is A2A missiles on an ESF, ground targets are just meat for rocket pods (even dual burster max dies faster to rocket pods then he can kill an ESF) and unless you are fighting a complete idiot you will never, ever kill an aircraft with a G2A weapon making it the most unrewarding job in the game (which is why you don't see many people unlocking G2A weapons). A2A rockets will consistently net you kills because you can chase them down when they run (but you are still better off unlocking rocket pods instead and cert farming till they nerf them)