Can I change from Nusach Ashkenaz to Nusach Sefard? Absolutely Not!! There are only 2 authentic Nuscho’os:- Ashkenaz & Sephardi; These 2 authentic Nuscho’os have both been around for well over 1 Millennium.
The other Nusach is so fabricated, that just look how many variations it is infested with, because it is not genuine, and hence there is no consensus about the correct version for Sephard. Somebody decided to invent it approximately 300 years ago, and deviate from Minhag Avoseinu b’Yodeinu.
Havara:- A Patach can never be the same sound as a Komotz, therefore Komotz must be an “O” sound as in the word “hot”.
There are only 2 correct Havaras for a Cholom:- Either an exceedingly deep “O” sound as in “Go”, or an “ou” sound as in “house”. The “oy” sound is absolutely 100% flawed/invalid, because then how does one distinguish between a “Cholom” on its own verses a Cholom followed by a “Yud”?