Console region doesn't matter all. However, your PSN account region does matter - so if you're buying the EU version you need an EU PSN account associated with your account, not a NA one. You can't mix and match, so since you've started out with the NA version you have to buy the NA version of SB too.

I'm using a Japanese PS4 with a UK (EU) PSN account to play the EU version of the game on a Japanese server. To give a practical example. Japanese game codes won't work on my account so I can't use them, even though I've had a few, and I had to create a UK PSN account after buying the UK version of the game because my Japanese PSN account couldn't register it