I used 2.1, it has all the same flags, and I did turn them on because they're not enabled by default. It's completely insane without those flags, but even with them enabled I still ran into many surprises. For example, like the other poster mentioned, its handling of variance is simply appalling.

And no, Flow is MUCH more sound, I have worked with both. Flow's limitations tend to be false negatives (code that should ideally work does not compile as is) whereas Typescript's are false positives (fails to detect type errors).