>>15498708
>How much time does it take for one blind playthrough on average?
I'd say about two hours, depending on how dogshit you are.
>do I need to finish the game one time as each nation to see all the content or something like that?
Yes. But it gets better, there are also interactions between commanders but there are three on each side per battle and only one of them gets to speak as-per an arbitrary priority list. Some of those interactions involve recruiting an enemy commander at the start of or end of the battle. Shit's fucked. Grand Edition also lets you play as the bad guy so get that.