(should probably keep this one a thread about your cube project)
Separate PBs + expanders don’t need to do anything with the expander channels, thats only if more than one is on the same physical data line. Firestorm (Apr '23 edit: and/or the new sync feature) don’t know/care about that level. Each PB is basically running free, independent of the others, with animation time bases kept in sync. Likewise when you map them, each PB will have their own slice of the map.