SPICE is bad anyway. And only meant as a way to install the VM.
I suggest you use either a Parsec or Moolight/Sunshine setup for GPU accelerated Desktops with sound.
TN need to add a lot of missing devices and options to the VM system, which I think they will do now there is an Enterprise market for it as well as the home server guys.
Not if you use RDP and the VM OS is Windows. It will create a “Remote Audio” device and you will have playback on your desktop.
VNC and Spice emulate a locally connected VGA card - you cannot do all of the nice things with that. Just like you cannot copy&paste or play back audio from a physical monitor that is three buildings away.