Most of the "code" is pretty self explanitory. Point-based entities are indicated by having an "origin" field, whereas brush-based entities are indicated by having a "model" field.
You can do pretty much anything you want as far as point based entities go. You can change all their field, you can make them completely different entities, and you can even make new ones if you want (though lights won't light the world, as that's built during the map's compile).
As far as brush-based entities go, you can only change their immediate properties. You can't do something like turn a door into water, and you certainly can't change their origins [unfortunately]. HOWEVER you can add new brush-based entities by treating them like point entities. This is good for adding triggers or teleporters. Just remember that ingame they will have zero size, so you will have to run directly into them, or just line up a bunch of them
But to actually answer your question:
Look for game_player_spawn and game_player_connect. Odds are, one of those is triggering a game_player_equip that gives 100 armor. Just take the entity out, if that's the case. Take out the game_player_equip while you're at it just to keep things clean.