Here is a small "how to" cap MaxFPS in Steam version of Quake Champions:

- go to Library
- right click on Quake Champions
- select Properties
- click on Set launch options... button
- add --set /Config/CONFIG/maxFpsValue XXX, where XXX is any preferred FPS value, i.e. --set /Config/CONFIG/maxFpsValue 125

Also you can enable FPS counter in Steam: Menu - Steam - Settings - In-Game - In-Game FPS counter - Select any preferred item apart from "Off" - OK