Okay, help me out here and check my logic.
I want to buy the console bundle (JP). I plan on giving away the Switch itself as a Christmas gift, and I'll preload my Switch with the code. However, I'm assuming that the code in the JP bundle will only be usable with the JP eShop. I have a Switch profile with its Nintendo Account region set to Japan (it's actually a friend's account), so I'll have to use that person's profile to download it. However, I should be able to play the title on my own Switch profile. I also plan on getting a copy physically for my collection when I'm in the US for Christmas. Since Switch games share save data across digital and physical versions, my US cart version should be able to begin using the save data I've started on the JP digital version. Additionally, I'll buy the fighter's pass on my own US Switch profile, and should be able to use the DLC with both versions of the game.
Basically, I wanna confirm that two different copies from two different regions will only contribute to one save file and that I'll be able to basically treat the two of them as one copy. For DLC purposes as well as just to ensure nothing wacky will happen down the road if my friend gets his own Switch and makes that his primary console.