I think your information is quite outdated. The HWC overlay planes are heavily used, you can see this trivially just doing a 'dumpsys SurfaceFlinger' or grabbin

I think your information is quite outdated. The HWC overlay planes are heavily used, you can see this trivially just doing a 'dumpsys SurfaceFlinger' or grabbing a systrace/perfetto trace. When it falls back to GPU composition it's very obvious as there's a significant hit to latency and more GPU contention. The overlay capabilities of the modern Snapdragons are also quite absurd. They support like upwards of a dozen overlays now and even have FP16 extended sRGB support. Some HWCs (like the one in the steam deck) even have per plane 3D LUTs for HDR tone mapping (ex https://github.com/ValveSoftware/gamescope/blob/master/src/docs/Steam%20Deck%20Display%20Pipeline.png https://github.com/ValveSoftware/gamescope/blob/master/src/d... ) The composition is bandwidth heavy of course, but for static scenes there's a cache after the HWC in the form of panel self refresh.