I basically agree with him, while have some differences in specific.

For DPOS, monitoring witnesses and removing bad or lazy witnesses are very important. In this sense, 100 seems too big to make dynamics in the top active witness list. I think around 30-50 is a good number.
As he said, 30 votes can make the witnesses dependent on few whales, as Steem is now. A further problem is 30 is too many for individuals to evaluate and monitor witnesses. The bigger the number, the psychological burden will exponentially increase. 1 is good number too, but I personally prefer 3-5, which is similar to the number of "very close relationship".