Would this be relevant to running MC32 on Pi 5?
No, PipeWire doesn't really make any difference. If you care about bit-perfect audio output you should avoid PulseAudio (and PipeWire) as they go through the system mixer and use one of the ALSA outputs that bypasses the system mixer (e.g. hw:, front:, etc.). The limitations you speak of were likely regarding PulseAudio, not ALSA.
Only thing about your requirements to keep in mind is if you plan on listening to DSD content, that DSD bitstreaming does not work over HDMI. You'd have to convert it to PCM (which would be very taxing on a relatively weak Pi 5, especially multichannel DSD content) or connect to the AV processor another way (e.g. USB) or avoid that content altogether.
Regarding install, just install Media Center via the installJRMC script, it makes it very easy.