there was many threads about how to limit down the fps to 60 because of speed issues and gameplay changes that occured on high frequency screens (such as 120, 144 hz screen, any screen above 60hz actually)
So I guess I finally found the way to limit down this fps, anyway it works for me.
So you can only make it in your build (nw.js export project).
To do it, first you need to make your export, and then, you must add a small modification in your package.json file.
So, first open your package.json file, using 7-zip File Manager, this way :
then you should find this folder with many files, where you must find the package.json file (one more time) and open it this way, by clicking "see" or "edit" (because sometimes, "open" do not work here), this way :
then you'll find like a text file, where you must add the argument "--limit-fps=60" in the "chromium args" section (anywhere is fine), like this :
then you just have to save carefully and close this file and it's ok, your game will run with a framerate limited down to 60 fps !!
good to know too, that you can also remove the devtools (the stuff that appears on chrome when you hit F12 key) by adding "--disable-devtools" too, can be useful to not bother the users of your game.