Hello there Si — it’s been a while. That’s a pretty comprehensive summary you’ve written and I think you’re making good selections. I’ve come at this from the other side — I’ve just built a house from scratch which meant I could run cables wherever I needed and minimise the need for wireless. I used Loxone which is fairly proprietary in some ways but does have various interfaces and can send and receive HTTP commands so can be made talk to other things with a bit of work.
The house still isn’t finished but we’ve been living in it, with the smart home functions increasing as I set it up, for 5 months or so now.
The thing you’ve missed/challenge you still have to deal with is physical buttons. Unpocketing and unlocking your phone and opening an app to switch on your lights is *not* convenient (believe me — we’ve still got a couple of rooms without switches) and getting switches to work with conventional UK wiring is non-trivial (see https://shkspr.mobi/blog/2016/02/smart-lights-dumb-decisions)/ ) but once you’ve got a buttons you can interface you can do some nice things with them.
I’m running two Logitech Harmonys now — one for the kitchen and one for the living room — and they’re excellent. The physical remote is often more convenient than the app but the ability to use the app when the remote’s across the room (or the battery is flat) is handy. The cheap non-touchscreen Harmony remote is possibly better than the expensive touchscreen one (I’ve got one of each) — it’s got a physical number pad, you can perform any ‘advanced’ tasks from the app and the touch screen is too easy to hit by accident when trying to use the physical buttons.
I didn’t realise you could trigger Harmony from IFTTT. Annoyingly Logitech have Harmony pretty locked down — you can’t add your own HTTP commands to a Harmony activity so I need to add in IR interface to my Loxone system (and obtain a random remote/create a dummy device) to get a button on the Harmony to turn down the lights. Some of the audio companies are a lot better — Yamaha will provide the protocols for IP control of their AV amps which is nice. My ‘leaving the house’ command from a triple press on the light switch near the front door turns off the kitchen audio, turns off all the house lights and turns down the ventilation/heating.