

Wiktionary suggests both “fixing to” and “fitting to” are used synonymously. Fwiw, in Tennessee, I only ever hear “fixing to”. As someone who learned English outside of the southern US, it makes little sense to me also. But what makes even less sense to me is people saying “trying to” to mean “want to”.
I’m the same. Best I can do is read as fast as a kinda fast talker? I do not comprehend how a person can read much faster than speaking.