Indeed, scholars suggest difficulty in deciphering text during the Hellenistic period and early Empire (caused partly by lack of spaces between words in manuscripts) precluded reading silently to oneself. Reading seems mostly to have been done aloud in formal settings after periods of difficult practice. This applied equally, apparently, to both Greek and Latin texts.
One of the reasons we know this is that Julius Caesar was remarked in a couple source as being able to read texts upon first encountering them.
Apparently, given people wrote about Caesar’s ability, and the knowledge survived, it must have been quite a rare talent. (Even if the accounts are fawning exaggerations, and he couldn’t actually read texts at first glance, we can still conclude the ability was very rare.)
I had never really thought about the implications with respect to early Christianity, but you make a fascinating point about performance. Reading in ancient times was dramatic (rhetoric classes were a total physical hoot!), so we can absolutely presume Paul’s readings, whether or not he was present, must have been filled with drama.
I never looked at it that way before.