This might be a stupid question, but since they’re both running, doesn’t that mean they’re installed already so all I have to do is disable one? Or is manjaro-pulseaudio a specific version of Pulse Audio that I don’t have installed?
It is a meta-package that installs all of the required pulseaudio packages. Likewise, there is also a manjaro-pipewire package.
However, pulseaudio and pipewire cannot be reliably used together, because they will compete over the hardware. As @ishaanbhimwal says, you must install one or the other, and uninstall or disable the one you don’t want to use.