"There are several open restaurants."
Translation:Det finns flera öppna restauranger.
I think it's just to have a distinction between when something has a certain trait and when something exists in a certain state. After all, "Det finns" literally means "it exists," so saying "Det finns flera öppna restauranger," is literally saying "Several open restaurants exist," or "There are several open restaurants." If you were saying something like "The restaurant is open," you would use "det är" because it's more for when something possesses a certain trait.
Is there a difference in saying "öppna restauranger" and--if possible--restauranger öppna"? If you were looking down the street and you saw several possibilities to choose, as opposed to if it were after 10 p.m. and you were expecting to see most restaurants closed already--and several were indeed still open?