@taersh :-
Mk I and Mk II (or Mk 2, if you don't know Roman numerals!) are not, repeat NOT official, "proper" designations for AppImages. They are how I, personally, think of them to myself when comparing early and modern AppImage builds.
Mk 1's are early AppImages from WAY back when the format was relatively new and the developer stuff had not yet been created in a "user-friendly" format.....in addition to which, "opening" an AppImage to see what was inside it required the use of a special binary tool to do so.
For "Mk 2's" - modern AppImages - it seems the build process is now greatly simplified, and many additional command-line "--switches", etc., have been added to make managing them even easier. Which is great for would-be devs and the community in general, but it's had one negative side-effect; lots of would-be 'devs' are simply re-packing .debs & .rpms WITHOUT including everything necessary for them to run in a totally 'self-contained' manner. Instead, they're still hunting around the system like any normal package, looking for dependencies. A properly-constructed AppImage should NOT be doing this, since it is supposed to contain absolutely everything that is needed for it to run......on whatever OS you choose to use it.
Mike.