Opera singer here. IPA is indeed as coarse grained as you described in the latter sentence. Accents can definitely leak through. Practically speaking most opera

Opera singer here. IPA is indeed as coarse grained as you described in the latter sentence. Accents can definitely leak through. Practically speaking most opera singers do not use it, and are expected to take two or three romance languages in college. Accents tend to be ironed out mechanically because you want uniformity (when singing in a chorus) and good projection of the phonemes onstage.