I have to admit i very seldom use pre cuts, so it's a good thing I don't mind the cutting process. I'm afraid I also must admit I don't bother to do test blocks,,, I just jump in & start cutting & sewing. I've never really had any serious problems using this method.
I don't decide about the borders until the main part is finished because my quilts have a tendency to grow when I'm not looking.
I just like to go with the flow & not get bogged down by too many rules.