Hi there, @Abel_Navarro 
Unfortunately, it’s impossible to autoplay video at the moment. I am sorry!
However, this is a nice idea and we’ll try to think about it in the future.
Just to clear things up: do you want all video thumbnails to autoplay once the page is loaded, or you want them to play on post hover?
As for the full post display, we’ve got a solution 
-Display full text without Read More button