You can force a specific Proton version on each game, though I’m not sure (off the top of my head at least) if that would help with not installing duplicates. Iirc best practice for using Wine for games is to have separate installations to avoid having conflicting dependencies, though I’m not sure if Steam does that.
Also, GE is short for Glorious Eggroll, which is the name of the dev who creates custom Proton distributions. People refer to these distributions simply as Proton GE or just GE. Ref: github.com/GloriousEggroll/proton-ge-custom