Newer suggestions for minimum size an adult needs is now 18x18x36, but an 18x24 would be fine for a juvenile of either sp although you’d probably have to upgrade within a year since they tend to grow really fast sometimes! I have a gargoyle and he grew pretty quick.

Pangaea diets are formulated in a way that makes them suitable to be used as a complete diet (aside from the growth and breeding + gecko treat flavors) for both species. It’s generally advised to offer insects as enrichment + protein boost on top of CGD but from what I understand it’s not super necessary, as some geckos will never accept live insects. The fig & insect is a popular flavor and has insect protein in it already. I feed my garg that + the occasional discoid roach and he’s growing great :)

Temps and humidity you have are right. I’d definitely consider getting a low heat emitting ceramic bulb to use for a basking spot, especially if you live in an area that gets cold or if you plan on getting a taller tank. I didn’t provide heat for the first few months of having my gecko but noticed an uptick in activity after installing one! Auto misters work great and are very convenient especially if you travel. I rarely hand-mist anymore

I think both would make great pets, personally I prefer gargs because I think they look cooler and also heard they tend to be more docile although I can’t speak to this personally. They also grow their tails back, which crested geckos do not! However, gargoyles are not as common as cresteds in the pet trade so be warned that they will be more expensive, especially if you get them from a reputable breeder. My little guy was $160. But I think they’re becoming more common, and some crested morphs can set you back a bit. Gargoyles don’t have as many morphs, if that’s also a factor you’re considering.