There are actually five Ancient Mew variations. 
Here an outdated article from 2012 covering the first four versions.
Although I don’t collect Mew personally, I do collect the Ancient Mew variations in PSA-10 and have four of the variations (will also grade some ©2019 versions myself soon to complete the quintet):
But congrats on the cards you already have. Especially the Ancient Mew I (corrected) in PSA-10, since that one was the most difficult to find and most expensive of the four I have above.
And when you decide to start collecting all Mew cards, you could contact @skinst (who collects all English and Japanese Mew cards, including sealed cards and products) or @lof102 (who collects all Mew cards in all languages), whom are both big Mew collectors here on the forum and who could probably provide you with a list of all existing Mew cards. 
Enjoy your stay, and good luck with your collection goals!
Greetz,
Quuador