Anecdotal evidence: historically I have a 60% winrate on US West servers (~40-70 ping) and only 50% winrate on US East servers (~110 ping). I've played on EU servers and it is absolutely miserable at 200+ ping. If I had to play regularly on anything above 110 and I'd probably drop to 45% or 40% winrate.
After a certain number of games you get used to it and start anticipating. It's not perfect, that's for sure, but it's definitely doable. Or are you talking about 5k+ MMR? In that case it is trickier, of course, but I know even pros managing to do it :)
Admittedly, it's not exactly the same as the setup in this article since it's not streaming over the internet, but I would assume that as long as your latency is low and bandwidth is high, you'll have no problem with this setup.
Game server <--> Amazon <--> Home
From a pure latency point of view, this is probably not an issue. However, whatever events you see on screen, the game server sees you reacting slower, because your keyboard basically has a delay of 20-30ms (Home --> Amazon).
Maybe, it depends a bit on the game you play, if this has any negative consequences or not.
Edit: This could be somewhat compensated by the faster connection of Amazon <--> Game server (just assuming that it's faster than a connection from home).