The opposite, slightly adjust your bricks to suit. Dont change the dimensions of the structure.
Yep.
Take into consideration the corner bricks. Have a look at the reference below, you can see on the far left how they overlap nicely on the edge, towards the center they are cut to shape, this happens on site often and brick layers have to adjust as well. My rule to keep things consistent is corner overlaps should be either a full or half brick, and the rest can suit the reference image I have attached.
