45-50% its going to be the sweet spot for you to be able to keep a clean, mold free enclosure, but still get good sheds. 60% would be the higher end of what’s necessary. Anything beyond that and you’re looking at a reduction in air quality, which can lead to respiratory infections.
It’s worth pointing out that consistent sheds are as much a factor of internal hydration as external hydration with Ball Pythons. They will drink more readily of fresh water so if you’re doing a couple of water changes per week, you’ll never see bad sheds, even if you have poor humidity.