I don't like to trim down -- it seems extremely difficult to do accurately, and is so time consuming. I cut fabric to get the exact HST size I want without trimming.
So far I have only worked with patterns (quilting for three years). If I ever get through all the pattern quilts I have planned, I'd like to try designing and piecing in the way of Ruth McDowell. I don't see myself ever creating geometric patterns of my own. I have not had the patience to learn drafting.