How to connect two walls as as T or as a corner I put all these walls together, snapped their ends to the other faces and merged by distance but I have all these overlapping faces.  I tried to use a boolean tool to remove them or to merge edges but it either deletes the build or claims there are no intersections.  I've already started this over multiple times.  There are two colors now so I can see the intersections and overlap better.  There has got to be an easy way to get these parts to stick together and not have all that overlapping mess inside.  Help!
Dissolve those faces that are overlapping, select them and the ones you want them to connect to and press Ctrl + E --> Bridge Edge Loops to fill them.