If I’m understanding your initial question, no recommended method exists for installing a Desktop Environment (DE) as a Snap package in Manjaro.
As you correctly surmised, the ISO files in question are non-official; being created independently by forum member @Jim.B (as @Yochanan has indicated above). Any queries about these ISO’s will need to be directed at their creator.
To be clear, this was unclear. If you wish to have useful responses to your questions, please ask better and well structured questions. Can you perhaps rephrase?
I should imagine what you call “copious amounts of totally irrelevant information” was given to assist you in creating a Support topic that would maximise the chances of it being understood and actionable by those who might wish to help.
A reminder that the Manjaro forum has strict rules that one agrees to by virtue of using the service; and a long memory.
Ad hominem targeting Moderation staff or other forum users and brazen disregard for forum rules is not tolerated.
The links given were indeed relevant, as are these;
Regards.