Yeah, the DS port is basically the way to go nowadays. It actually pretties up the game in a few ways, namely some of the map graphics.
Only if you want them to though. Though you probably will end up with heavily similar loadouts, partly becasue the way wanzers work you basically can make one unit do most anything, but if you play up to characters’ skills there will be some amount of variation. Still, FM1 certainly doesn’t have the variation in weapon capabilities or create the kind of restrictions that require different builds for different tasks like the later games do. I also wouldn’t regard it as rock paper scissors since it’s doesn’t really have anything countering anything.