Currently I don't have any mmWave sensors outside of my ecobee thermostat so I haven't gone as far as creating lights based on presence. Currently I just use timers, adaptive lighting, and have a couple night lights using PIR sensors and a timer. I have been wanting to get some mmWave sensors but haven't found anything that fits the bill as I want something with an ambient light sensor, mmWave sensor, temp sensor, etc. I have seen the Everything One from Everything Smart Home but at $65 each, I'd be spending a few hundred at least.
Also if you ever want to go back to your RPi, you can use an SSD as your boot drive. I have mine running off this so that I don't have to use a crappy SD card.
Not sure of the compatibility, but you might look into Shelly relays to automate old fixtures, lights and switches. They just wire in parallel to the switch and sit in the electrical box behind it. Also they make GU24 to E26 adapters. I had to buy some for our outside garage lights which are also GU24 sockets as well.