I'll be flying thru JFK with a 10 hours overlay, would I be able to do 2 or 3 of the routes? How long is each route?

Go to their website book a tour as per your convenience. The bus tour starts near Times square, New York,and you need to collect tickets from there office which also beside there. I hope it helps..

https://www.bigbustours.com/en/new-york/new-york-bus-tours/

Buses come every 15 minutes. Each route takes an hour and a half approximately