At 60fps vsync, Snack cannot kill more than 60 people per second during deathmatch… 😉
Anti-aliasing is indeed the first thing to turn off, that’s an excellent tip. Another thing is grass! Setting it to normal really saves a lot of fps. It’s also easier to aim as the grass sometimes obstructs the view (for example in the Avi mission on the island). I found the “extended distance” options also very demanding, especially during in-game daytime, so I tend to turn those down a bit.