Automatic DVD to .iso copy after disc insert with two drives
I've managed to solve it very easily.

After comparing Mac DVD Ripper Pro, MacX DVD Ripper Pro (don't confuse the two), RipIt and AnyDVD for Windows. I decided to use Mac DVD Ripper Pro.

It has a setting to start automatically after inserting a DVD and ejecting it after being finished.

I run two instances of the app using open -n /Applications/MDRP.app. Since MDRP picks up the first DVD it finds, and the first one won't be available, the second instance will pick up the second DVD drive and vice versa.

Output .iso is not a bitwise copy, since MDRP takes care of the copy protection (at least CSS was no problem) but played well in my tests with VLC and Kodi (on my Media Server).

Only thing I didn't find were log files, but everything else I've been looking for is solved this way.

If you prefer video_ts output over .iso you can do the same thing using RipIt, RipIt also in-officially supports ripping from two drives at the same time.

Note: I haven't yet tried ripping DVDs protected with Sony ArccOS, UOPs, and Disney X-project as mentioned in the comments. CSS protection worked.