I'm not sure there are answers to any of this, but I'll put it out there anyway. If for nothing else, just to see it all in black and white.
What I know: I'll be biking cross country this summer, from east to west. My wife will be driving along the way. I can cover around 100 miles/day. We'll be doing a mix of camping and motels, but she needs to find internet access most days, to catch up on work.
Route? It was originally going to be Trans-Am with a mid-May start. For a lot of boring reasons, it's now going to be a mid-July start. So now I'm thinking Northern Tier. NT pros: slightly cooler weather, maybe a bit less humidity and the fact that I prefer the northern part of the country. TA pros: 600 fewer driving miles to the start in Yorktown (vs. Bar Harbor), tons of info from previous TransAm riders, plus I love Oregon and like the idea of finishing there vs. Washington.
(To that end, I've thought about doing the NT to Williston, ND, then the Lewis & Clark from Williston to Missoula, then the TA to Florence, OR. But that appears to add about 500 miles to the trip. Not sure if I can make that work.)
Again, I'm not sure there's a question in all of that. But if someone sees something I'm missing, or thinks any of the above is just plain stupid, I'd love to hear your thoughts.