Games are often limited to 60 Hz by the "Game Optimizing Service" app built into the phone, unless Samsung specifically marks it as compatible. This can be fixed by disabling the app, but that also gets rid of the do not disturb while gaming. It is sad to see Samsung limiting their own hardware, and instead should just have a 60 Hz option for incompatible apps (like the change app aspect ratio button). This has been an issue since launch day, and it is annoying to see it's still around.
fps may vary depending on your phone's condition and interent connection strength.
different from 120hz.
ur game might be at 30fps, and still be 120hz.
for example, if ur internet is slow, your game can display at 30 fps. even though u set at 120hz, u will only see 30 fps.
also, not all games support 120hz, developers have to update to make it compatible