When I draw 4 walls, how can I get the ending of wall 4 to neatly fit with the starting point of wall 1?
Looking at the image below, my problem is the left hand corner. The right hand corner is not boxy. The right hand side corner is an automatic join when I click several times to place multiple walls.
Double click on the start point (the starting wall will be colored when you approach it), or afterwards, use the Plan > Join walls menu item (see this article).