Thanks to justonegamr that we can see what's different in the English version! One of them is the 3rd option in the Title Screen, displayed "Import". Once you get in, you'll take to the screen from pic up there. Looks like you'll need to upload the JP save via Cross-Save coz it uses that feature for this method (It has to be on the same system).
Re: JP save import to English version! Nope, the cross-save data you upload is tied to your own PSN. This is great news, though. I wasn't looking forward to having to redo some of those Extreme perfects. How thoughtful of Sega to even do something like this! F2nd's localisation as a whole seems very well done.
The guy said in the comments that transferring a Japanese save through cross-platform is possible. So you can use a Japanese PS3 save for the English Vita game.
I hope this means similar for edit songs..! To be able to play without worrying about which version they were made for would be super great, especially since on the vita it is difficult to play edit songs because of how the edit mode is DLC and that means resetting the vita to switch accounts and dahhhdhdhahhgrahh... Does this import feature means that the trophy list is going to be shared between versions?