On /ɢʁ/: "The phoneme _g_ is a voiced 'non-aspirated' uvular affricate. Schooling (1981:49) says, 'The term "non-aspirated" is used to indicate that even though there is some friction, there is no breathiness.' Note that Stimson transcribes _g_ as _r_." This is from Proto-Eastern Polynesian *l, which is from Proto-Polynesian *l and *r.
Glottal stop is contrastive in word-initial position in addition to word-medial: /age/ 'to be open', /ʔage/ 'wave'. The sources of glottal stop are Proto-Eastern Polynesian *k *ŋ, and in a few cases, *l *w *m. PEPn *ʔ usually goes to 0, but in some cases there are doublets with 0~ʔ: *ʔata > ata 'to appear momentarily; cloud; shadow; reflection; experience', ʔata 'indication of the presence of anything'. In some cases, glottal stop is intrusive.