Simple Bundles has 1 really big limitation: you can't edit/add/subtract a product variant and expect the bundles to automatically update. The only only workaround is to recreate the bundle (meaning having to reupload all the images/descriptions) or edit the .csv file and reupload it. Either option is complete completely ridiculous. Imagine having 100+ bundles all sharing 1 product in common, and if this product now has a new variant there's no seamless way of getting all the bundles to upload automatically. Nightmare scenario tbh.