I’ve only used the larger Octopots: 6 gallon reservoir with 6 gallon fabric pot on top. My goal is to keep things simple in my garden. Fewer waterings and the ability to leave things unattended for days if I need to go out of town are the big advantages - that, and the plants just love them and explode with growth! There is a smaller Octopot available - around the size of the AC Infinity model mentioned - which I believe @Papalag has used. You can also hook them up to a larger external reservoir with the right plumbing connections, but I’m striving for fewer points of failure…
The plants can get huge! Here are a couple Consumption x Chocolate Thai with a Lemon Wookie V2 on the right filling a 4x8:
The manufacturer does not recommend super soils in Octopots. I use straight ProMix HP (High Porosity - lots of perlite) for media, and feed Jack’s nutes via the rez.