In my small test using a Valve Index, I saw zero difference in visual clarity or performance one way or another. Setting the render scale to 500 yields no change at all from 100 (in the SteamVR app with MSFS scale at 70). I’m only seeing change from the in game render scaler.
Does MSFS not use this area of SteamVR? I’ve locked my frames at 30 through SteamVR so they are talking.