If you’re overwhelmed your approach is probably to blame. Rather then look at the “big” picture look from “outside the box”. For example:
Perimeter doors/access points to your home: Contact sensors or motion detectors
Lighting control via: motion sensors /mode/or time.
Alerts and response: push notifications, sms, siren.
Home monitoring devices: cameras, thermostat, fire/smoke/CO2 detection, air quality
Look at each location of your home starting from the outside. Play the what if game and go from there. It’s not hard at all and if you do it yourself you have added bragging rights with all of your friends
If I were in your position my primary concern would be the overall structure wiring. I did mine after buying. I still have an entire floor to do. The other HA (home automation) stuff is all basically plug and play or peel and stick.