Mark has made a number of ORAC videos, some general, some specific, e.g. “Orac 2.0 for Raspberry Pi” should be interesting:
MEC should come with the pisound ORAC module, but the service has to be configured to auto-start manually once (it’s explained in the video). Unless the Pico turns out to be too power hungry, you should be able to directly plug the Pico into the Raspberry Pi 4. Would be worth a try. (I still have a Pi3 with pisound with an Alpha which worked)
P.S.: You could also experiment with the power limit for the USB ports: https://www.raspberrypi.org/forums/viewtopic.php?p=594183#p594183