100 hz is somewhat equal to 100 fps, not in a direct way but yea...
it is like 100 oranges is equal to 100 tangerines lets say
(Its a quote from somewhere else)
Well as for your question, lets say on a 120hz you would be having the same experience, as 120hz and 144hz monitors are overkill for your frames per second output. so yes, your gpu is producing less frames than the monitor can actually show.
But to be honest it doesnt really matter as above 60hz or 60fps it seems almost the same for human eye. the important thing is to match the fps as much as you can with the refresh rate of monitor, in this case you are good to go.