As XCOM is pretty big title, I'm still considering this.
You see, bDisablePhysXHardwareSupport is an option with "mysterious" effect. I saw people claiming that hanging it gave them more advanced physics and FPS boost in games like Mass Effect or Gears of War.
Unless I see a solid numbers and actual benchmarks in XCOM, I'd rather not post it.
Just like Rise Of The Triad and Shattered Horizon, XCOM 2 can use GPU PhysX
Shattered Horizon never has working GPU PhysX support. There were plans, but no final result. At least, when I was playing it. As for Rise of The Triad, they actually had some extra particle effects, afaik. And an option to enable them through menu.
The game is listed on the Geforce site as a PhysX supported title
Right. Among other famous GPU PhysX titles, such asWarhammer 40,000: Eternal Crusade
or Arizona Sunshine
Hint. Those games are CPU PhysX only. NVIDIA's own list is highly inaccurate.