Good set up are ones that hold correct temps and have enough ventilation. Humidity is complex it should be coming from the evaporation of water from the water bowl and substrate. The placement and size of bowl will change the amount of humidity it releases. May try to use the humid air all critters with lungs breath out to get humidity up. This is done with very low ventilation and forcing the air to circulate. This IMO (and most vets...) is not a good idea.
Holding temps depends greatly on the ambient room temps. Temps are far more critical than humidity, all body functions are linked to temps. The problem many face is ambient air temps and cool end temps. Hot (warm really 90º is not hot to human touch) spots are easy UTH and t-stat usually settles this problem. Cool end temps are harder they are usually close to room temps professionals use racks in heated humidity controlled rooms so this is not a problem many advanced keepers do the same. But the rest have to fiddle to get it right. Enclosure type helps a lot. Tanks have lots of heating options but the open top heat is lost and humid air is lost too. Why I posted the side turned tank better ventilation than an up right open top. (hi and low allows hot air to vent and cool air to enter the lower holes) they also hold temps better and humidity better (humid air rises). A side turned tank reduces the heating options some but still has many options. (lights, UTH, RHP, CHE, and Lamps are some (most of the common ones) of the heating options available. A custom PVCx offers the most efficient heating (best insulation) and is often the best option for a cool room as they hold heat best and have a range of heating options. Custom built enclosures are far to varied to comment on. Good designs hold heat well and humidity well and are easy to heat poor ones are hard to heat. Often this comes down to material choice. Single tubs heat and cool VERY quickly (thin plastic is a really poor insulator) this is good to heat it but bad in that it cools as quickly as you do heat it. The ambient and cool end temps in regular room temps can be a problem. The cool end and ambient due to the poor insulation tend to keep the room temp. There are very limited options for a single tub. UTH basically and they are do not directly effect air temps. What makes a tub great for a professional with a heated snake room makes it not so great for a snake in the living room. They also look terrible generally.
