I like scrappy quilts but get uneasy if they're really busy. I think it usually works best to have some contrast in scale and color value, and if that's under control it really doesn't matter how many fabrics there are per se. As some have put it, your eyes need a place to rest. Having a balance between light and dark, busy and/or bright prints and some that are quieter and more subtle will give a quilt areas of focus. I like to use a value finder. Mine is old and just red, but this page explains the idea:
https://www.karencombs.com/page.php?ID=34