There's no such thing as a "GSX fps", that's not how Simconnect works.
The way Simconnect works, is that apps ASK to be called back at variable frequencies, depending what they need to do. Those frequencies are 4 sec (one time every 4 seconds), 1 second, 6 times per second and "Frame", which means at every frame, so the sim itself will call GSX ( and EVERY other app that has subscribed to the "Frame" event ) at every frame, no matter of high it is.
This means, to reduce the data frequency, you should lock the fps in the sim, which will in turn reduce Simconnect traffic and the update frequencies of all running apps.
Beyond atc did this and the animations was alot smoother when using motion smoothing in VR.
What they probably did, was to CAP their own updates, meaning not replying to all callbacks from the sim. By doing this, they reduced the amount of traffic over Simconnect produced by BATC in reply to the sim calls, to the benefit of all other running apps.
But while this might be a sensible approach with a non-visual application, it wouldn't work with GSX ( we obviously tried this years ago ), because GSX drives vehicles and their animation, so if we just ignored some calls if they exceeded a certain frame rate, the animation would be even more stuttering then they would be when the issue is just too much traffic over Simconnect, so the best solution is still locking the frame rate in the sim, because by doing that, you don't even need that all applications would cap themselves: the benefit would extend automatically to all running apps.
In fact, it would be even better compared with applications capping themselves, since with the fps uncapped, Simconnect will still generate OUTGOING traffic to call each and every Simconnect app as fast as it can, so the only benefit of apps capping themselves would be the INCOMING Simconnect traffic being sent back from capped apps, so it's only a partial benefit at best.
Instead, when you lock the fps at the origin, you are limiting all traffic, IN and OUT, to all running apps, without requiring any changes to any of them so, the more apps you are running at the same time, the more benefit you get by limiting the fps in the sim.
