Of note the CT36 AC can take the exact same HEPA filter that the CT26 and CT36 use. Which also includes the same wet filter. The HEPA "rating" for the dust collector is only important to a professional getting inspected by OSHA. Happy home owner can have the same thing by just swapping filters. Festool dust collectors also work great for water cleanup.
If you are only doing your own house and don't plan to grind concrete etc, choose your new dust collector by your needs in the future. Size can play a roll for some people.
Myself I have two CT36's with one being an AC version. Often I wished one was a much lighter dust collector, but never really found it to be a big enough issue to buy another dust collector. If I was a painter, then I would buy a Mini most likely. If I was looking at a CT26 I would just get the CT36 as they are the same with just a bigger tub, which means a bigger bag so I go through less bags. Grinding concrete the CT36 AC bags get very heavy!
That little Ridgid vac may not be designed to run in the vertical position you have it, as the bushings for the motor are most likely not designed to handle a side load. *shrugs*
You will REALLY enjoy the much quieter Festool dust collectors. The whine of Ridgid vacs is deafening. Get the Bluetooth module, and a 5 meter D36 hose to go along with whatever you decide.