There’s lots of hard-won experience in your post, which I’m going to have to bookmark and re-read more than once. Thanks!
Your use of sub-directories for YAML is particularly neat, and something I’ve been meaning to do after hearing Frenk give DrZZs a tutorial on YAML syntax many live streams ago. Groups are a similar simple idea which are likely underused.
#5 is interesting as I’m a Solutions Architect and believe choices are informed by understanding the trade-offs behind a product/ platform/ protocol. My own take on comparing Z-Wave/ Zigbee/ Matter/ latest shiny might therefore be of interest:
Of course there are exceptions. Z-Wave’s mandatory testing doesn’t always work - Fibaro’s FGD-212 early firmware connected well but worked functioned very badly and they force you to buy their hardware for updates!
Even after building custom automation hardware for years (BASIC script on a '286 plus triacs!), the ESP* self-build idea initially seemed hard work. After many Tasmota and ESPhome builds, they work well for non-standard things to automate, but are best used with mains power as WLAN is still too energy intensive for battery devices.
Careful though, as one moment you’re hitting BUY on a Wemos D1 Mini board for £3; the next there’s a shipment arriving with a 3D printer, filament, Octoprint server, IR camera, … 