3-4 contests sounds like a good number. I'm feeling a bit bad that I'm spending so much time on my current entry that I haven't had much time to do thorough reviews on other games.
Yes, I am in the same boat.
This is a good idea, and I would also wonder if it makes sense for a bit of slack as this one ends--so people can read the Best of 2019 contest game before they dive right into a new contest.
September and October worked well for an inter-site contest last year. Maybe I'll do some variation of that this year around the same-ish time.