I have made rag quilts with denim and those corner seams are really bulky.
What finally worked for me; sew up to but not through the corners. Take back stitch, then cut the threads and start on the other side of the corner. By the time you snip a wash the quilt, you will not know that you did not sew through the corner.
As far as the plush shifting, glue, or baste the blocks just inside of where you will snip, before you sew the rows together.