1. Can leos be housed in a rack system with just UTH (if not, what do you prefer to house them)?
Yes this is how I use to keep my groups. I did 1.2 in a 32 quarts tub

2. What would an average feeding schedule be for an adult leo (number of bugs and how often?)
Daily I found it best to have food available at all time, I used to keep a dish with mealies at all time and replace them with new fresh gut loaded ones every other day.

3. Could leos be kept healthy on a diet of only meal/super worms or with the addition of dubia (no crickets)?
Yes I use to feed mealies exclusively

4. How plausible is it that female leos (if the same size) could live together without issues (or would it be better to do smaller individual tubs)?
You can house females together just fine if they are the same size.