There is no technical limit on the number of property groups you can create. The useful test is whether your guests would browse the label as a collection.
Tags that do not need a group. A PMS tag without a group prefix still comes through as a plain tag that you can use for badges and filtering. Labels that do not need their own page or chip can stay prefix-free.
Keeping the chip row readable. Keeping the chip row under roughly ten groups makes it easy to scan, but more works fine.