I’ve seen you post a few questions about t206s. Most of what you are asking can be found (many times over) by just searching old net54 posts. As far as t206 backs - and some of us really love the backs (more than the fronts)- I recommend these two papers/articles:
http://www.oldcardboard.com/t/t206/i...al-edition.pdf
https://www.psacard.com/articles/art...ack-variations
Also, Derek Hogue, a member of net54, has a great hardcover book on t206’s and backs. He is at t206society.
As far as the best Matty, that’s up to you. The portrait is most expensive/valuable, followed by white cap and then the very common dark cap (one of the 6 most common cars in the set). They are all great. Find one you like and for a good price, and then get the next one. After you have gotten all 3 poses, try to get all the front/back combos (and if you go down that path, let us know if you ever re-emerge from that Bermuda Triangle)
Good luck!