It indeed locks your fps at the refresh rate of your screen. V-sync also makes sure that only complete images are provided to your screen, if your graphics card isn't done rendering a new image the monitor will show you the last complete
image the graphics card has rendered (60 hz = 16,67 ms per refresh done by your monitor).
v-sync gives some extra input lag, some people don't mind, others hate it. And it can cause some stuttering
Your TV panel may be 100Hz, but that's with the use of interpolation. That's not real 100Hz (The connection over hdmi is at 60Hz to explain it in a simple way). Best to turn that 100Hz crap etc off while gaming on TV (less inputlag), but most TV's automatically turn those things off when you have a gaming or PC option.
TV's have a lot of input-lag in comparison to PC monitors
GPU fluctuation is normal, percentage of usage depends on what you're doing in the game and what's happening around you