OK, I think that this Homekit stuff is pretty deep and much of this doesn't have a guide, but three quick things:
Homebridge insights are that this thing actually works really well. It's a simple node application and using a $50 Raspberry Pi is really the right approach from a simplicity and isolation point of view. So some notes on this, first is that I'm using the plugins for it and the Unifi plug-in and the Harmony Remote plug-in work super well.
The main tricks are that by default, the Homekit devices will end up in the "room" where it detects the Homebridge, but if you go to each device, you can click on the gears icon and then move it to the correct room. So for instance, we have two Logitech Harmony Hubs in two bedrooms, but by default, all the devices appear in the Basement where the Homebridge room is, so you have to go to each device and move them.
Moving around favorites and ordering in Apple Home only works on MacOS
For whatever reason, the iOS version of Apple Home does not allow you to order things, so go to your Mac and startup Apple Home. That version does allow you to drag and drop the various icons. This is most useful for Favorites, it puts all new devices by default into favorites, so you have to go to each device, click on the gear icon and unclick "Add to Favorites" which you can do on your iPhone,
But to move the widgets around, you go to MacOS Apple Home and do that there. Pretty strange.
Motion Alerts to Turn on HomePods when No-one is home doesn't work with Unifi over Homebridge
It is not obvious how to use automation, but basically, Apple really only allows two things when a motion event happens. You can turn on a light or you can play music on your HomePod. The use of this is that if you are not home and it detects something, you can turn the house lights on and turn some music on as well.
I ended up settings this as two automation because the lights only go on if it is dark and the playing of audio happens all the time. You can also set it to turn it off after so many minutes.
This is all pretty tedious to set up, so the best thing to do is to group your HomePods and your "security lights" into a single group, and then you can select the Accessory you want when you create the automation.
Sadly, this is one thing that doesn't seem to work right. When I get motion events from the Unifi protect, it will turn on the HomePods even if I'm home. Seems like the fact that it is a foreign device makes this hard to work.
So here's another request to Apple to open up the programming on these things, there is really a big matrix of events, conditions (like who is home), and then actions to be taken. It is about five lines of code, but hard as heck to do in today's user interface. Open document settings, Open publish panel.