Note that it does nothing to block DNS over HTTPS lookups. If your browser insists on going around your LAN's DNS setup, Pi-hole can't help you.
V3 introduces a hard limit on the total number network filters an extension is allowed to set and it's a laughably low number. Far below what uBO uses even on a barebones, default setup
v3 removes the ability to block, but not the ability to monitor. It doesn't make anything more granular.
Once again, I went stupid adding blocklists so the level of management previously required is kinda worst case-y and it is absolutely my own doing and since working through my idiocy it just works its magic without needing intervention. If you're more careful about not adding blocklists which say 'this will break things' (not hard) you'll be fine.