I've never done anything like that and chance you could give me the specific steps? Also will there be any downsides to running dual monitor like that? Like reduced gaming performance?
just connect to receiver...in nvidea control panel (im assuming display, im amd) there should be a place to enable what display you want as primary
now the rest i did in windows..right click, display settings.......scroll down to multiple displays and set it duplicate these displays...done
now right click the speaker icon click open sound settings..choose the av receiver...done
if its 5.1 make sure you right click the speaker icon again and set speaker setup to 5.1
and as for reduced performance...no i havent seen any (im on a rx590)
oh not sure if it matters or not but you can run a lower res on the receiver ( my main is at 4k but my receiver res is set as 1280x720)