I, like you have been on this journey also a long time and have gone in many different directions. I would say you definitely have the knowledge to go forward, but to simplify, from what I read above, my suggestion would be first reverse back to simplicity, don’t create your own models but use what others have created since all rigging is there. No need to reinvent….next ask Jay….he is a great teacher in animation….click her to his YouTube channel for free about animation using the free software Daz Studio… https://www.youtube.com/c/TheWPGuru/search?query=animation

your computer is plenty good to do what you need in my opinion. I think the cost of models would be cheaper then purchasing software to create your own characters, and there are so many to use and adapt to what you need.  I hope I understand your question and hope this helps. Let me know.