Modular buildings 1950 School

Hello Everybody. This is my work in progress. I’m making 1950 School building. I looking for suggestions and better way to make parts of school.
On 1st Screen the mesh consist of boxes (and i receive lots of Light map bleeding), 2nd i organize in one clean mesh and it solved the bleeding.
the UVWs (0) stretched to work with standard materials in UE. (<regarding to that i got a question: can i create a material that will work on UVW1? so i can create a custom material in Substance Painter?)
Any suggestion and tips are much o