When we brought our new house, we did exactly what you're proposing, using all Ubiquiti gear, but being already built, I had to retrofit it.
A UDM-Pro as the router & firewall, a 16 port switch in the house, an 8-port switch in our hangar (though I wish I had a 16 port here...), Cat 6/A cable to an Access Point in each bedroom, the loungeroom & kitchen, and an NVR with the Ubiquiti cameras' to round out the house. 6/A cable through a spare conduit to the hangar connected to the 8-port switch with an external AP for the backyard on the hangar eave, and a pair of AP's in the hangar with a few cameras here too. The Ubiquiti gear is exxy for "just" a home layout but if you want 'prosumer' gear with greater flexibility than stuff you can buy at a department store, I'd recommend it in a heartbeat.
You can certainly get by with just the UDM-Pro to start with as it has 8 ethernet ports itself, but if you want to add an NVR & camera's, you'll need a switch. Of course, you can add these later if you wish, and simply connect the AP's direct to the UDM-P and later run a SFP cable to the NVR if you choose. One of the best things about the Ubiquiti system is it is very scalable, and being one ecosystem, it's easy to add things later.