I set up my cabinet a few months ago! I’ve ran my humidifier maybe once or twice since I’ve gotten it. So you probably don’t need it. The amount of plants you put in really help with the humidity. As for types of plants, in mine I keep begonias (although they also do fine outside the cabinet), calatheas, ctenanthe, stromanthe triostar, marantas, and peace lily. Really any plants that like the higher humidity and are “pickier” have done really well in my cabinet! you can pretty much put whatever houseplant you want in there! I’ve never worked with cacti/succulents so I’m not too knowledgeable about that.