This is and always has been an interesting topic. Once with pitfalls. The first myth that must be dispelled is
TCP is slower than UDP. TCP and UDP have the same speed of transfer over the internet. Where the draw back is that TCP has safe guards for lost packets and data fragmentation. This will lead to a bottleneck. Often the bottleneck won't be a problem, but sometimes it can build up and that's where it all goes wrong.
For most real-time games. TCP is fine. It's only in high twitch gaming like Fighters(Street Fighter) and Shooters(Halo, CoD....) where the bottle neck is extremly bad. However RTS games and most other real-time will run fine with TCP.
However the link you show is an excellent source of information that WSS can stream data and then using a frame system reduce that problem subsantially.
However I wrote a shooter in C2 using Photon Websocket. My server on a an Acer netbook located in Vancouver BC Canada, was able to play reliable well with some one from Europe. However, a friend of mine located in Vancouver too. Had an extremly choppy experience.
So distance wasn't the problem. Also my shooter had no latency correction, dead reckoning or any advance stuff. All it implemented was a catchup move to system and worked really well.
Websocket is totally doable. However if you can use UDP you might as well :D
But there are examples of TCP being used for active competitive games like Guild Wars. I won't say TCP is better, but it's certainly usable.