You can load new styles into the 10 User Style slots as on the PSR-E453, but you cannot play styles directly off of a USB drive as on the DGX-660.
If by "editable" you mean the styles, there are no style editing capabilities on the PSR-E models as on the PSR-S models.
You can toggle the six style tracks on and off, and you can adjust the overall Style Volume; but that's it.
If you want to do any editing, you'll need to work on the style file with a utility program.
And if you want to edit one of the internal styles, you'll need to record the various sections of the style in a User Song, convert the User Song to SMF, use a utility program to edit the MIDI file and convert it back into a style file, then load the new style file into one of the User Style slots.
It sure would be nice to see the Style Creator and Song Creator functionalities added to some future PSR-E4xx model, but I don't expect to see that happen.
