Does flying on VATSIM impact FPS? Also do you have to change any graphics settings when flying on VATSIM? 

Nope.

Instead of multiple AI aircraft you see AI aircraft that correlate only to active real users connected.

There's no impact at all or any graphics settings you need to change.

 

All I have changed is to ignore Crash by other aircraft (can't remember the exact title in settings) because you can not control where "any" user may decide to taxi/fly through. :rolleyes:

It may not be due to negligence but simply someone connecting at the same parking position where you are at that particular moment.

 

 

Instead of multiple AI aircraft you see AI aircraft that correlate only to active real users connected.

 

Ah I see that is good then. What program would you suggest is the best way to connect to VATSIM? 

FSInn

 

Here's the installation guide (inside its support forum).

http://forums.vatsim.net/viewtopic.php?f=43&t=20466