Meanwhile, the Klingons put the nacelle inside their BoP. I guess they just YOLO it.
Design notes for the shows have said that nacelles usually work best in pairs and with at least 50% line of sight with each other, but they’re not hard requirements. The nacelles in TOS were supposed to be detachable in an emergency but it never happened on the show, similarly to the saucer section.
I think the explanation for nacelle positioning they ultimately settled on during TNG was something about the shape of the warp bubble, but I’m not sure.