Unifi uses MongoDB because somebody at Ubiquiti thought it was cool. It's not an open-source project, you don't get to see their IRC chat logs or commit message

Unifi uses MongoDB because somebody at Ubiquiti thought it was cool. It's not an open-source project, you don't get to see their IRC chat logs or commit messages. If you're uncomfortable with IPv6, you are right to turn it off. Learn it, become comfortable, then configure it properly. This advice holds for everything. Is it worth setting up RADIUS? Only if you want the experience. One of the possible functions of a home lab is to gain experience. It sounds like you want to learn how to do operations. It's always advisable to start by gathering requirements, generating threat models, listing resources, and then trying to construct a plan. None of this needs to be fixed in stone - as you research one thing, you should learn of alternatives with different trade-offs. Keep track of all that. There is never just one set of "best practices".