Adult males get a small rat each week (that about 60/70 grams), adult females get a small medium rats once a week 80 to about 120 grams (yes even my 3500 grams breeder girls)What size prey do you live feeders "max out" at meaning what is the largest live rat do you feed your snakes?
It can happen tubs offer a sense of security which sometime translate in the snake no longer using it's hide.2. I put my ball python in a tub and now she wont go in her hide.... Is that what happened to your ball pythons?
I recommend to house cresties individually when young, while you can house 2 or 3 geckos of the same size together, when young one might get bullied preventing access to food.3. Not a question but wow crested geckos are adorable.... Can you house a pair or trio in a 18x18x24
and can you house a baby crested in a 18x18x18? How long will it take for them to outgrow that? Well i guess this was a question
As adults so long you do not house 2 males together, and the animal you will house together are of the same size you will be fine in most cases.
I would also not recommend to house a male and a female at all time, 1# you do not want the female to breed before proper weight, 2# when she does start breeding you want to give her a break (remember female will lay 2 eggs every 4 weeks even long after the male is removed)
Hathlings until about 10 grams can be house in a 12 quarts tub and you can house a group of 2 or 3 adults in a 40 gallons breeder. For hatchlings you do not want to put them in an enclosure that is to big if you do they might have issues finding their food.