remember too that there are various types of scouts for MLB teams.
The "best" scouting jobs get to scout major league games -almost exclusively. These 'advance' scouts will watch other teams their teams are going to play, or make special trips to check out potential trade candidates - particularly at this time of the year.
This is a pretty good gig - well paying, lots of travel -lots of watching MLB games.
That said - the 'lower' scouting jobs are much more hectic and don't pay as well. They watch minor league games (which some of the upper level scouts will do as well - again centering on trade potential), but these guys have crappier hotels to stay in, often take buses from site to site..you get the idea.
At the lowest level are scouts that watch amateur games - HS and college games in preparation for the MLB draft held each year.
As far as the "in person" vs "TV" question - I could see TV-only working to scout pitchers to a degree, and position players batting - but you really do see a lot more in person, it's not even close.