So when looking at the prints you want to see what will give you the best variation in your blocks. For both I would cut about 2-2 1/2 at the biggest. Most people know how I like small pieces. I would even consider cutting the black and whit a tad bit smaller. If you are still going to do a wall hanging it won't add that much more work.
On florals I usually measure a med sized flower for the size. It is totally subjective to who is working on them. Once you do one or two you get a better idea what to look for choosing prints and cutting sizes.