If I uncap, will that make any saved files I have SUPER huge? In other words, are there any downsides to doing this?
What saved files? You mean like recordings? I assume those record at a constant bitrate independent of your framerate. I don't see how this could affect your actual save data for progression in any way. As far as I can tell there are no downsides. Been playing with it for a couple days.
Some people will prefer to keep it capped at 60 fps because a fluctuating framerate bothers them. I find it is not a problem at all as long as the minimum stays over say 80-90 fps. Just turn settings down until you are in the 90-100 range if you have to I guess. Obviously you will need a high Hz monitor.