I am going to answer my own post, for the benefit of anyone who may want info regarding the same problem, since I have just completed my trip...

I booked all my tours using Get Your Guide, although the tour operators said they also advertise on Klook.

For Day 1, I took a walking tour which gave me a good overview of the city, and then a food crawl later that day.

Furano tour gave me a good overview of the area but I wish I spent more time at Farm Tomita to enjoy their pastries and more of their soft serve. Melon buffet was good. Furano melons are good but not life-changing as they imply them to be. For those who live in the US, often the Costco Tuscan-style melons can be as good, if not better. I heard that Yubari melons are better than Furano melons but that tour sold out two weeks in advance!

Half day Otaru was fine. 8 hours was overkill - unless you planned on soaking up all the seafood at Otaru market. If you think Sapporo seafood is good (and it is), I feel Otaru's is even better. And the shop owners in Otaru are very nice and personable compared to those at Nijo market.

I did not get to see Asahikawa or Hakodate or the Blue Pond. Will save that for next time.