Sorry, I'm in Sandbox (so it seems to be hard coded).
I'd recommend buying this to anyone that has a potato for a PC and wants to play a more stable version of KSP.
I just tried flying something at 300 parts (298) and the frame rate dropped to 5-10 fps so that's probably why ha.
BUT that was in an atmosphere... And I was hitting mach 1 with my big lifter quite quickly with no load so... there are the aerodynamics calcs going on there too. It might perform better in a rendezvous/docking manoeuvre with 300+ parts, but is there a hard coded limit there too? I could try science it and come back with an answer.
In addition, looking at the rendering there doesn't appear to be any AA. A full list of graphics settings would be interesting to see too (texture resolutions etc.).
Controls: different, definite learning curve, but absolutely doable.