I generally keep 4-5 adult rats, sometimes with a few <1mo olds in 110qts (these are my "main" living tubs). I clean tubs at least once a week. I find disinfecting weekly helps a lot with odour and healthy environment. I use vinegar/water solution.

For grow outs only in 110qts, I guess it depends on how much you want them to grow out lol. If I'm not keeping the rat, I cull around 5 weeks. So an entire litter or two would be fine until then in 110qts. This all depends on how much space you want to give them and how often you want to clean. I can't really give a concrete answer bc other factors like food, amount of ventilation, stress, etc will all contribute. Don't overthink it too much. Once you have litters on the ground you'll learn how to eyeball it.

I'm in Ontario but I can't help w online shopping, I do all of mine in store. Do you have a TSC in the area?