I think the most important factor is comfort in the saddle over weeks of 10+ hour days. That means a more upright position that a TdF bike, but a comfort bike won't be much help in a week of heawinds. Unless you bail on the weather, you won't get to choose it. I don't find the frame on my MTB all that comrortable over hundreds of hours, they aren't designed for that so why should they be.
I had a Peugeot touring bike back in the 70s, and it didn't come with any BOs, even the downtube shifters were on a little band. So there isn't any reason to discount a bike just because it doesn't come BOed for racks or fenders.