Never payed hs2 but this guy playing gives a good indication of whats going on
http://pinball.org/videos/gameplay-videos/high-speed-2-the-getaway/

As far as Embryon goes, there's no story line like on 90's dmd's, basically you hit targets down for scores, the centre captive balls enable you to spell embryon and light a ball lock. After a ball s locked you need to knock down the right hand target and then hit the captive ball to release a 2 ball multiball. The multiball is pretty difficult to get but pointless in that there is nothing special to aim for during it. You simply have to balls on the playfield and thats all. However its a nice game to play for a 1980 machine, i like it.