Any difference between preot & popă?
"Popă" is rather informal. It is not the nicest way to refer to a priest as "popă". However, they mean the same thing and you will hear many people using this word.
Nobody here that hears something like "e" between sunt and doi in the fast text?
Yes, the fast version has these anomalies sometimes for some reasons. So, you are not going crazy. Well, maybe you are, but not because you are hearing this extra sound.