Put the epic launcher installer on C:, set it as the exe to run in the Lutris settings, run it and install.
Change the executable to the exe of the installed epic launcher. Run the launcher, install and play your game.
I’m using a separate wine/proton prefix for each game. This allows to appy custom proton settings and workarounds per game. The epic launcher is about 250mb so it doesn’t waste that much disk space.