There's not much point "keeping your hand in" for curved GPS approaches. You end up flying Flight Directors only, which isn't any good for your scan - and for RNP AR operations, most operators require at least one AP must be engaged prior to the Initial Approach Fix (IAF) (According to a/c equipment, RNP AR may be approved to RNP 0.3 or RNP below 0.3 (lowest certified RNP is 0.1).)