Lutris prompts you (when installing from the repository store) to add a series of optional parts, one is gamemode, another is mangohud, there are a couple of audio libs too if memory serves, they are all useful when running things via lutris, gamemode is the most needed, it allows you to isolate the game and prioritize system resources when you launch a title allowing the title to run a little better, subject to the game of course.
EDIT
This information may me different subject to the distro you are on, im running Manjaro and this is how it works for me.