Recently I had a problem with low volume in music players on Budgie.
I fixed it by removing wireplumber state folder and restarting pipewire, wireplumber and pipewire-pulse.
Question to Budgie users, what do you have in .local/state/wireplumber/stream-propertie file at the line that starts with "Output/Audio:media.role:Music=" ?
You should see something like this:
Output/Audio:media.role:Music={"mute":false, "channelVolumes":[1.000000, 1.000000], "volume":1.000000, "channelMap":["UNK", "UNK"]}