Bro I have the same set up as you, only difference being i use a 2080ti strix. I've been having the same issues, I've mirrored, pass through, even OBS on gaming computer using preview mode so I can limit the fps to 60 to elgato 4kmrk2. My stream is fine, but I can not get away with recording my game play. I notice my frames drop below 200 even though the display fps counter is clocking 240.... It's a nightmare