Just to complicate things... you might want to look at PocketBook's offerings. Looks like they're sold in Sweden.
https://pocketbook.se/se-se/catalog
As for screen size... almost all my reading has been done on a 6" screen and I think they work fine. Definitely gives you a more portable reader. But I do have one (old now) Kobo Aura HD (6.8" screen) and I don't mind using that one. I have tried a 7.8" screen and, for me, it's too big and unwieldy. (Opinions differ on all of this.)