Known issue: DCS World may show double frames in Pimax headset, at all times, regardless of CPU/GPU load/latency.
Solution1: Import and run DCS World directly through PiTool.
Solution2: PiToolSetup_1.0.1.109_R193
To run DCS World directly from Pitool, it may be necessary to disable DRM modules (eg. F-5E), and start SteamVR before launching DCS World. Doing this will still start SteamVR, so overlays should still be usable.
Much thanks to @SweViver videos for demonstrating this technique working with recent Pitool versions.