Other than the digital swag such as OST, Novella, etc., is there any other compelling reason to buy one edition over the other?

Price wise, at this point the Hero edition is the most interesting but I can't help but think I'm missing out by not getting the Royal edition.

Any advice would be welcome.

My opinion but the advantage of Champion Edition is the soundtrack and the collector's book in the Royal Edition. You can listen to the music here to at least judge if the Champion Edition would be worth it.

I'd just get the Hero Edition, but also get the DLCs. It DOES affect your main game, you will get access to more abilities, some of which are kinda mandatory for min-maxers (Apprentice Sneak Attack).