Bangor, ME to Elkhart, IN - Suggestions

Another vote for I-88 / I-86 across NY.
DrewE - Duff's is now open in Rochester (the old Friendly's down the street from Jay's.)

If you are a pizza lover you will be very near Goshen and must stop HERE.

Anytime we are in northern Indiana I will drive an hour out of the way for their pizza.

That sounds like the fast but uninteresting and toll-heavy route. Nothing inherently wrong with it, but not what I would choose myself.

Nearly as quick and free of NY tolls is taking I-88/I-86 across the southern part of New York. The Corning Museum of Glass is a good stop along this route and rather more interesting than its name might initially suggest. Watkins Glen isn't too far away, either.

Taking US 2 across to Montpelier is also perfectly reasonable. From there, one has a few options. The one I'm most familiar with is crossing to New York at Crown Point (at the southern end of Lake Champlain) and then taking 9N south to 8 to NY 365 and then getting the Thruway at Verona. There are other routes through upstate New York that are also good; given enough time, meandering along the St Lawrence would probably be a lot of fun.

US 202 to 9 to Albany also should be perfectly reasonable.

Letchworth State Park (south of Rochester, NY) is a fabulous stop for a day or two. Nick Tahou's in Rochester is a locally famous greasy spoon (emphasis on the greasy), the originator of the "garbage plate." I was rather more fond of Jay's Diner when I was a student at RIT, on West Henrietta road--fairly traditional diner fare, but done well and with a good variety. They've spruced up the decor a little since then, but thankfully the prices are still fairly reasonable. (Parking across the road in the shopping center is probably easier with an RV.)

When we went to Buffalo for wings, my group of friends would generally go to Duff's Famous Wings. The warning on their server's aprons is to be disregarded at one's own peril. ("Caution: Medium is hot; Medium-hot is very hot; Hot is very, very hot.")

These mapping programs usually just choose the fastest route - using various estimates of speed based on road type. That tends to favor the freeways, even if it is a bit longer. Switching to a 'shortest route' option might go through the mountains. Also try turning off 'freeways/tolls'.

And on GM, try dragging the route around to see alternatives. Note how distance and time varies.

It can be tricky to match a route with dining spots. Can you tweak the route and time so you end up a diner at lunch time? Or camp close enough to use it as a breakfast or dinner stop? It's easier to combine motels and restaurants.