Is the playback maximum 60 fps? Say I want to make a 100 fps video, can I not preview it at 100 fps over the timeline? Playback over 60 fps always displays "60 fps" on the playback screen.

Meaning I can create 1000 fps videos but I can only preview it in 60 fps in blender? Any work arounds or addons to fix this? I'd want up to 100 fps playback.
The maximum fps that can be played back will depend on your computer and the complexity of the scene in blender.

The syncronze playback option tells blender to play every frame or drop frames to keep playback in sync with time. You set the fps at the 100 you want in the final output video, then if the scene can be played at 100 fps it will be, otherwise frames will be dropped so that playback will be in sync timewise.

The interface preferences can be set to display the fps that are being played, when frames are being dropped the fps will be drawn in red.