How to confirm whether the pipewire real-time process has been successfully started
If you followed those commands successfully, then it is working 
echo "== Tasks that believe they're the most important in the universe ==" && ps -eo pid,cls,pri,command | grep -E '^( *[0-9]+ +)(FF|RR)' | awk '$4 !~ /^\[/{print}'
shows which tasks are being scheduled under RT.
Spoiler: Pipewire isn’t scheduled by RT 