whats more effective for an orthodox, the overhand right or the right hook ?

no offence meant but this is poor logic.
Lots of different ways to torque a right handed power shot from an orthodox stance, most awkward of the two will be a standard right hook since it neccesitates either over-stretching or 'squaring up' to some degree.
Both orthodox and unorthodox tecnniques should be learnt and practiced in sparring , either shot or variation thereof will have it's pros and cons dictated by the opponents actions during an exchange.