I’m using Plasma Wayland as well. Games do do that where they minimize on focus loss but I’m pretty sure they did that on X11 as well (especially since they mostly are using Xwayland) and I haven’t had any connection problems in multiplayer games when tabbed out. I’d have to see if your problem happens for me with virtual desktops, I rarely use them. And the music thing doesn’t happen at all, the screen locks and turns off and music/the youtube video/whatever keeps playing as normal.
What distro are you using? I’d chalk these problems up to a distro bug…