I don't know if AttractMode (AM) will ever come out of experimental in Retropie. I doubt it but you can ask on the RetroPie forum. I would never install AM using the RetroPie menu, it causes a lot of issues if you really want to run AM as your primary frontend (FE). I (and others here on the forum) recommend installing RetroPie, and then complile (FFMPEG and then) AM manually and run a script like I showed you to get it all together. Unless something has changed, the RetroPie menu install doesn't give you FFMPEG video decoding in AM and it also overwrites many things when you do an update and it doesn't stop there.
The Pi is great if you want to spend little money to emulate. There are cheap PCs and NUCs that can do much better for only a few dollars more. I haven't touched a Pi for emulation in a couple of years. I only looked at it for fun to get my friends that were jealous of my PC setup a cost effective emulation system.
Today if my only choice was a Pi and I wanted AM as the primary FE, I would install a minimal *nix OS then advmame and retroarch (RA) manually and then AM manually.
If you're only using RA then you can just run RA setup to add the controllers in AM. You really didn't go into details of you setup and needs/desires for other controllers. I use a cabinet where the controls don't change but people are cleaver and if there is is will, there is always a way.