So the bottom line here is that a business can refuse to serve you if you have a mask but if you have a lawful exemption they cannot refuse to serve you, even though they are not allowed to ask for proof of exemption. If they refuse to serve you if you have an exemption, they can get fined. So basically the best thing would be for a business not to enforce the rules.
More proof that the mask rule for everyone simply exists to create a herd mentality, where it becomes socially unacceptable to wear a mask and so the mask rule enforces itself. It has nothing to do with health. Masks do not prevent the spread of a respiratory virus and cause more disease by making you breathe in bacteria, funghi and allergens.