I don’t think that the current tools will be using it internally, since this would require the tools actually supporting the CLI launcher, and in the best case we would have something like the proton config in steam in every tool separately again.
I think that you will need to have your launcher installed, but you will have this new launcher as your entry point, from which you will start your games using proton from the linked project.
But - it’s a PoC right now, maybe both ways will be possible.
From a wishful perspective, it would be super neat if this new launcher would hook into the installed regular tools, and automagically make those use the preconfigured proton runtime it brings. Shouldn’t this be possible using LD_PRELOAD?