Humidity control demands a lot of good air circulation! The "safety" from too high humidity is great airflow. Not a wind tunnel, but breezy.
What I found confusing starting out is the VPD chart. Its valid. Its pretty cool actually because in the zone during veg you can tell its right. But how the heck do I follow the VPD chart and run LEDs at 84 degrees and have humidity of 70% without mold in flower?
Well..maybe with airflow and the right strain. A gent above does it, isnt the only one and if you can do that awesome. But you dont have to in flower. The plants once mature enough can handle RH lower than the ideal range. As you ask...yes they transpire more to make up for the deficit. Yes they use water faster this way. But caution as JD says, there is a range it must be in. The general rule is 40 to 50% is good for flower and above 50% is the danger zone.
In most of the natural world, humidity or water content above 50% is conducive to mold growth...it requires spores but thats not usually hard to come by! They are everywhere except a clean room.