Haven't seen the thread

10 seconds isn't really bad. The server on time.windows.com is known to sync time even worse.
For the others I don't know, but I guess they aren't any better. The problem is, since the sync is done automatically, you never will be sure if the time shown on your computer is as accurate as you would like it to be. That's because it's a matter of how many "computers" update their time at the same instant. Therefore after sync it can be worse than before.

Myself I never tried, but theoretically you can enter whatever server suits you (maybe some of them windows won't accept). Be aware there are also servers which want to charge for the service provided.

Most countries count with some universities or other institutions which provide that kind of service, you will have to check locally. Those aren't that busy and therefore it might result in more accuracy. But as I said before, you never will know.