I had to delete #5 but essentially it pointed towards
https://www.rootschat.com/forum/index.php?topic=863488.0the above goes into detail on the Grouping process that I use.
Back to the topic in question.
R G 1 certainly looks the prime one to start researching, if only because they have a family tree which in turn may offer clues.
The big issue with Ancestry DNA matches is identifying them, and having enough hints available to put the match in a tree.
I managed to ID my Great Grandparents via a 240 cM match and a family tree of only two hence your matches are very workable and initially they look promising.
The key here IMO is to Group them and include the shared matches in the Group.
I’d also send messages and await responses, I try to make messages intriguing which should help to elicit a response.
Uploading DNA to other sites can help but with My Heritage they will want a fee paid to unlock the DNA Tools that they have. This site has given me three close Second Cousins who helped to break my brickwall via contact with them, and that is without using the DNA Tools available.
To learn more about Grouping search the Leeds Method and read the details, using Ancestry Grouping feature is very similar as is the method that I use and explained in the linked thread.
Good luck.