It depends on what you have to work with really..
Is this a lung room? Are you venting out? Dehumidifier location..
Simple way if you have AC and dehu in the room, is plug each extraction fan on a separate sonoff TH10 or TH16 with the sensor in the tent and have the sonoffs on automatic mode where they switch on the fan above a certain temperature. Mind you, the sonoff can be set to automatic for either temperature or humidity but not both, so you cannot set it to switch on for something like: (temp>28 AND humidity>60) or even better (temp>28 OR humidity>60). For that you can create a "scene" with those conditions but you can only trigger other devices and not the TH10s (or TH16s) or flash any sonoff with a different firmware giving you greater flexibility.
I currently run a single extraction system for 2 tents. I have a single powerful fan and carbon filter encased in a wood box that is connected to 2 tents. The fan vents the box that sucks from both tents, into the room. I don't vent out of the room. This is a lung room with AC where the dehumidifier (constantly runs at 45%) is located next to the intake to the flower tent. I have a temperature controller on that intake with the sensor inside the flower tent. I pump cold, dry air to keep the tent at 27C/45%. By the time the dry air reaches the VEG tent, the humidity rises a bit to 50%. Perfect. A controller can go on that intake as well. Again, the sonoffs can be triggered by either temp or humidity, not both. I trigger on temperature and rely on the powerful dehumidifier and distance from intakes, to keep it down.
I have another sonoff TH16 monitoring the temp outdoors (out of the blocked window) and once every 24 hours, replenishes the air in the lung room with fresh air from outside. My room is not completely sealed and I am not running CO2.
Last sonoff is acting as temperature safeguard. My flower lights are run through a TH16 with the sensor in the flower tent and its set to switch off above 31C and switch back on below 29C. If for any reason I suffer a thermal event in the tent, the lights switch off and I get a notification almost immediately from the Itead app. -VERY HANDY. saved me from messing with thermal switches on the LED builds.
Another irritating thing with sonoffs, but certainly not affecting its operation, is its losing connectivity with the router for a few seconds while it reconnects, like, a lot! Half the time to go in the app to check out the temps in the tents, one or more of the sonoffs with be unavailable, reconnecting.
To sum it up, you are the only one who knows your room and what affects what and what can be controlled. And the sonoffs you can only do so much with the stock firmware.
Hope that helps