By the way, I have also used STEAM's overlay to measure the FPS, however, whenever I enabled this option, there was a lag and a performance drop in some of the games while playing, if not all.
Not sure about you guys, but I have experienced this in FAR CRY 6, DOOM Eternal and Borderlands 3, because my fps was tanked while gaming. After disabling this feature, both the games ran much better without any hiccups/stutters.
Some STEAM users have also experienced FPS drops from 72 to 40 FPS, or 30 FPS on average, while gaming.