Mine are not quite as different in size as yours, but they are still quite different.
Stickers eats all her pellets in one sitting too. What I did was just lower the amount ( I give what I usually would have given Powder, the larger one, solo) and Powder gets less than he did solo, but he eats a lot of greens, so not worried about it. Otherwise Stickers eats too much and will get fat. lol
For greens they get their salad together, but since West is sensitive to greens, if she stays that way you could give Zeus a second salad in a different room. My two don’t mind being away from each other a little during the day. Sometimes mine have their salads separate if they are feeling like being in different rooms a lot that day.
For my litterboxes, I have two in their room – one is HUGE and one is smaller, Stickers tends to use the smaller one.
For cage, no idea… I am horrible at picturing what measurements look like.
as long as they both have plenty of room to run around, multiple litter boxes, can both stand up etc I would think it’s ok.