I guess you are saying level Streaming when you say building a region of the level…but thats totally different obviously I am talking about the changes that we make in particular part of your level (which is obviously gonna be in camera view) no matter its lighting or its color or it could be anything regarding changes but to see it in final build quality all I wanna say why do I need to build the whole scene I could just render that image and see it as image (Camera Region) that will save lot of time …I am putting all these point because when I was building “Particle Effects” project from unreal marketplace it was taking long time sooo definitely rendering camera region to take a look how that particular part looks in final view will be helpful for sure…another point is sometimes you might put your Qualitysettings to medium or low (not all the time epic when scene is heavy) so at that time you can render image to see how it finally looks but as image.
Forget that wireframe that I have shown in above image but imagine only that scene which is in that camera view and instead building whole scene just render that camera view…cause obviously I am working on that area which is in camera view only. This is just gonna be helpful thats all I know