They make a chart called VPD vapor pressure deficit, it is based off temp and humidity, during most of the grow the ideal VPD is around 1.0. You can find these charts all over the grow sites just find one and download it or print it out. VPD is the ability of the plant to transpire in and out of the stomata on the leaves. Just think of it as being able to breathe better.
I put up a post on my grow journal last night, a picture of my fan controller that also calculates VPD.
I have never run a de-humidifier, a humidifier a AC unit or a heater in my tents, but I have a unique situation where I have a heating cooling duct run to a coal room that is pretty small in size, 16’x6’. Tweaking the vent easily keeps things in the green zone. However I do run 6 fans, my girls wave in the breeze 24/7. I think great air movement is far more important that a perfect VPD.