OP here. I called ecobee and got great answers immediately from them. Their customer support is really good.

They said the both the Taco and Honeywell zone controllers work well but recommended the homeywell because of how its transformer is set up. Makes wiring easier.

I can have one thermostat location and have it respond to sensors setup in appropriate locations in the rooms that need it. It can also run the fan via air quality monitor (VOC) although I may end up doing this via home assistant via a dedicated co2 sensor.

I went with the inovelli switches but just checked out the site really liking the Lutron blinds. Thanks for the tip.

Thats really good to know. I ordered Blues but wasnt aware that it could be converted. Thanks.

Awesome thanks for the advice. Id seen conflicting info on zwave vs zigbee for switches. One of the main things was wifi interference, but i live in a remote place and dont have a ton of wifi devices or outside interference. Also ill most likely be running a ubiquiti ap cause i use ubiquiti at work and am comfortable with it. Should be super solid.

I dont care about karma but i do like to see a users history, something i apparently cant do on mlem. Not sure if thats site-wide or just this app. Without that i wouldnt be able to confidently use the buy-sell communities that i did on reddit like knife_swap or watchexchange.