DHCP is a really stupid service for the most part. Unless you are working with multiple subnets or have some very specific settings you need to pass to your clients, it’s probably not worth it to manage it yourself. I don’t want to discourage you though! Assigning static IP addresses by MAC can be extremely useful and is not always an option on routers. If you want static names and dynamic addresses, that is really where you need to manage both DNS and DHCP. It really depends on how and where you want names to be resolved.

Setting up your own DNS is worth its weight in gold. You can put it just about anywhere on your network (before your gateway, after, in China, whatever.) and your network won’t even know the difference if setup correctly. You can point BIND at the root servers and bypass your ISP completely if you want. ISP DNS services suck ass, so regardless of you resolve yourself, or forward all name queries to your anon DNS server of choice. It is the service to learn if you want to keep an eye on where your network wants to talk.

Your Unifi USG must play nice with your own server, by the laws of DNS. There may be some nuances when it comes to internal protocols like WINS, but other than that, it should be just fine.