Regarding the 1st, I know some people have special views & get hot like wood being drilled on hearing this; so don’t @ me. However, posting my view here since more than one person asked in the past few days. Yes, there are regional peculiarities of recitations & substratal effects (particularly strong in some kali~Nga traditions). However, I don’t think these are serious differences. Looking at the totality of the surviving traditions it may be said, broadly there was one ancestral recitational mode that has 2 variants:
- where every long svarita was duplicated (RV, SYV-K, AV);
- where only those before consonants & sentence ends were (KYVs). This type (probably both modes) go back to when the Aryans first conquered India & probably stemmed straight from a tradition practiced on the steppe.
The mAdhyaMdina tradition is neomorphic with the loss of this type svara rendering at some point.
The nambu RV version is not a hybrid of “north” & “south” but simply another case of ancestral svara degradation (except kampa) followed by some kind innovation – the peculiar triplications. It is however possible that the conserved mode was overlayed on lost styles because of what we see in the surviving prAtishAkhya literature. However, neither nambu-s nor mAdhyaMdina-s are really following any such ancient convention.