About a week or two ago, I've been having a recurring issue while using my Quest 2 to play PCVR games using the Link Cable. My frame rate is fine when I start up Oculus Link but as soon as the Oculus Rift Home loads in my frame rate drops to roughly 2-3 fps (I've checked this using the Debug Tool with Performance HUD). If I start up a game or load into the SteamVR environment, everything is back to normal except if I use the Oculus button on the right controller to open the overlay, with causes the frame rate to drop again and making it unusable.
Hey there. We found a handy link for you with other developers who can provide insight HERE. As for the Link cable, if your graphics card is up to date on its drivers, you may not run into this issue.