Yes, it is possible to memorize lectures and talks on the fly. There are people who learn it from zero in a few years. They are using memory palace.
Yes, it is possible to memorize fast with aphantasia. Mark Boyanowski got a world record for solving 43 Rubiks cubes blindfolded (he needed to memorise around 430 words in 40 minutes for that). He has aphantasia. Here he explains how he uses memory palace (Roman rooms) without visualisation:
