Do you think the voice actors are up to date with the manga? Like they wait every week for a new chapter?
Some voice actors actually prefer not to know about the events ahead of the recorded episode.
While others read the manga in order to prepare themselves for the future recordings, probably not every week though (i.e. read Tankobon volumes, instead of Jump)
the anime they watch the episodes they voice act in?
Personally, I don't think they do. Maybe here and there, but at least not regularly considering how most of the voice actors tend to have a very busy schedule.