By Mix systems I mean something else, AfA One is a "pure" OS 3.9 BB4 with the addition of AfA OS libraries (AROS For Amiga), when you try it you can verify this.
Systems like Coffin include libraries and system files that belong to various OSes and this results in incompatibilities
Mixing OS 3.1 or OS 3.2 with OS 3.9 runs into many incompatibilities, many of which have been discussed many times.
Regarding AROS 68k, no AROS 68k software can run on OS3, as you know AROS 68k executables are "ELF"
Caffeine I don't know the latest version, but it is supposed to include AROS 68k and OS3 libraries and files, this of course is a mix that I particularly dislike, because then it is no longer a true AROS 68k