From a quick read of the code, it seems like all this does is shift pitch; it doesn't change resonance or anything else that affects how your voice sounds. So it's great for sounding like a chipmunk or a demon, but not that useful for sounding like a different person.
Looks like it uses libsox internally. You can also use command-line SoX utilities to get the same effect. For example, this plays your microphone back at you, pitch shifted and with a delay:
play '|rec -p pitch +400 40 delay 5 5'
> There's very little accessible documentation of Linux audio stuff.
The classic information-through-IRC these days.
* Make loopback devices that are always there for headphones/mic -- software doesn't handle connection/disconnection well
* Keep all your processing in carla (i load it with systemd as a user unit on login)
* You still need some way to control "pulse audio" (even though it's pipewire provided) for per-app volume control, profile selections, etc, so you probably want pavucontrol for that.