Kraeg Minett 2 weeks ago

I can't speak to all of these, but I went to the Acropolis twice in early September. The first, on my own, was just after 8am. I bought my tickets online and had the place mostly to myself. There were likely another 50 people there but it's large enough that it seemed sparse.
When my wife finished her seminars, I went back up with her the following day, but not until late morning. Again, we bought tickets online so we missed having to line up to get the tickets. But the Acropolis was like the video above, very crowded, very slow moving.
I think the lesson is, like everywhere, the earlier you go, the quieter it will be.
And buy tickets online beforehand wherever possible and you'll skip one of the crazy lineups.