You know when I was building my room I was asking a lot of questions on here too. And I changed my mind a lot on what I was going to do. But I am really happy with where I ended based on the culmination of other members opinions and my own experience and of course some math/science to make sure everything checks out.
sometimes the cheapest thing to do spend a little money (like on an AC) and not have to do all the crazy work around to make a cheaper alternative work. Growing a huge amount of weed is already hard work without have to check that all parts of a crazy complicated fan system are working. And trust me I know what that feels like as I was running a vented setup on two 4x8 tents using outdoor air and it was a night mare with outdoor temperature and humidity swings (welcome to Ontario).
Are you going to use a light controller? Woth that many lights it starts to be cheaper than a multiple timers and sensors. A trolmaster setup can control lights and fans and ventilation to keep temperatures in line. I was pricing out a setup using different cheaper inkbird and sonoff controllers. But when you actually work it out the Trolmaster gear Barry cost more and you don't ah s to mix and match anything and you can control all the parameters of your room from your phone. Not to mention the data logging letting you view your humidty and temperature spikes and problems. It can dim your lights for you if temps are getting out of hand.
I’m gonna use a heavy duty contactor board similar to this (only pic I cud find)
I’ve used a custom unit Pretty much the same as this before and it works fine, however I would like to have 1 dimmer for all lights that could be wall mounted.
for the venthilation lately I’ve been using ac infinity cos I really really like the interface
for humidity I use the g.a.s vpd controller, during mid to late flower the dehumy runs constant and then humidifier comes on and off to keep everything stable, I don’t like switching dehumidifiers on and off lol