Alright, after 16 days with not even a single reply to my post, I assumed that not a single rider here has no prior experience to any of the three rides I outlined above. So just to share: I did the Bay-to-Bay ride last Sunday. It was 98% flat indeed and a century was doable given the conditions that day. However I only did the shorter 76.8 miles.

So to those who are planning to join this event next year here are my observations:

1) Route was along Maryland's and Delaware's major roads with 45mph and above posted speed limits. Even though the shoulders are wide and well-maintained, the fact that vehicles can travel at that speed and even greater is not for the weak-chested.
2) The 76.8-mile route is an out-and-back type, meaning you'll be riding on the same route going to and back. I personally prefer a loop-type so I get to see different sceneries. On the other hand, the 84.6-mile and the 104-mile routes took a different route in going back, passing through the town of Chestertown which was not included in the 76.8-mile route.
3) No lunch food at the finish line. This was a surprise because the other previous events I took part this year, lunch or at least some hearty snack food were included in the fee.

I'm relieved I answered all the questions myself. And this was my first-and-last.