the 7700k is "the fastest" CPU as it has the highest clock speeds and the most IPC (to my knowledge)
which for gaming is just what you need.
however if we're talking about CSGO, we're talking about a game that's several years old and runs perfectly on an LGA1155 i3.
for video editing the single core speed and IPC don't matter so much as the load can be distributed among several threads. so the more threads and physical cores there are, the better. that's why a 6800k beats a 7700k for video editing although being clocked almost 1 GHz slower.
until Ryzen the 6800k was the best CPU for this task as it provided 6 cores and 12 threads with clock speeds fast enough for gaming and a price that's bearable (compared to the 6850k or the 6950X)
but now Ryzen is here. the 1700X provides the same clocks as the 6800k, but 2 additional cores and 4 additional threads while being cheaper
compared to the 7700k you get DOUBLE the core count and DOUBLE the threads
of course a Ryzen 1700/1700X won't get you as many FPS as an i7-7700k on for example Crysis or GTA V as those games only use 4 threads and are more or less perfect for an i7-7700k or i5-7600k
which doesn't mean that you can't play them. the Ryzens are still pretty potent in this games, the 7700k is just a bit better
but if your focus is on video editing rather than gaming, I'd much rather go with a Ryzen chip.
Coming from someone who loves his i7-6700k very dearly.
but I'm not sure there are ITX boards out already
so if you're looking to buy today you might be bound to Intel