I have both versions of the Agfa Rondinax tank, 35mm and 120. I don't use them regularly, but they do work fine, The film is processed on a conventional reel with normal chemicals, the only difference being the mechanism to wind the film onto the reel in daylight.
The volume of chemicals is less than in a conventional tank (just comes helf-way up the spool, which is held horizontally), so you have to use continuous agitation and watch that the dev and fix are sufficient in their activity for one film. I've not checked, but I doubt that it would be suitable for color processing for those reasons.
I also used (many years ago) one of the mini-tanks where the 35mm film was processed within the cartridge/cassette using a special monobath. I remember that it worked, but not really good enough for regular use. You had to take the film out of its cassette for final washing and drying.