I'm a little conflicted as to how I'm supposed to use the "backstage" models. Does anyone know of any of the Portal 2 maps that use backstage props (mainly the props_backstage\triple_wallpipe_corner_*.mdl variants), so that I can get an idea of how they're used in Portal 2? Thanks.

I can't view the model right now, but it sounds like it's meant to be some infrastructure stuff that are usually used in small areas behind the scenes (like pipes). (Not in a test chamber). The BTS folder is more for large areas I think. Look in other maps for reference of what props you're meant to use if you're still not sure, but you can always interpret if you want to use the specific model for a reason. There shouldn't be too many precise decisions in detailing, and usually, it doesn't matter.

Thanks, ended up using them in some smaller "BTS" hallways.