Hope this doesn't end up as multiple repeats, seem to have a bit of an issue posting today.
My solution is to cut large and trim to fit. For either the snowball or the Square in Square, your center square would be cut correctly/precisely. The setting triangles would be cut an extra 1/4-1/2" larger than called for. So for example, if the directions call for 3" squares cut in half along the diagonal, I'd be making a 3.5" square. Slap them on easily and then use a ruler or template to trim to the correct size. For me the sewing goes so much faster the trimming doesn't add any more time than being precise in the first place -- but my accuracy is better! Plus, I was already handling/checking my subunits and decided I might as well make it worth the time.
20-30 years ago I'd probably give an audible sniff in disdain over "fabric wasteful techniques. I've watched and done tests and the extra 1/4-1/2" I add has usually never needed more than an extra row of whatever width of fabric. Now I consider the speed and ease and accuracy well worth a tiny bit of fabric, and when using strip cutting techniques there are always bits of unused fabric anyway.
Plus, 20-30 years ago I didn't have the vision issues I have today. For me, cutting big and trimming down is the solution.