Agree on the Yangon to Mandalay route. On the central road it's long stretches of flat uninteresting nothing. I bailed at after Yangon to Bago, to from Bago to Mandalay by train. Only interesting was partying on the train with military. Seriously fun. They're actually nice people.
I did - Mandalay - Myingyan - Nyaung-U - Meiktila - Pyinmana - Toungoo - Pyu - Nyaunglebin - Bago - Yangon. That was the west road to Bagan and was an interesting ride.. But,, I only rode 60k from Bagan At a drink stop a police turned up and told me I should get on the bus to the center road. Then two military with big guns pointing at me escorted me to the bus. Seemed a prudent thing for me to do. They were close and personal.
On the ride from Pyu I had passed a few oil facilities, some military looking places, some curious places, and a lot of appeared incarceration facilities. Think a fair assumption as I met many of them working on the roads. The many villages had never seen a foreigner.
I got the impression they didn't want me to be there. And that I shouldn't have been.
That was several years ago but even with the big changes (?) some things won't change fast. The old ways are heavily imbedded in their culture. Much will be kept out of sight. As I apparently saw what I wasn't supposed to.
It will be better now, but I only once had a problem with accommodation. In a town there was only one hotel, and it was a military one. And me being not I had to go to the next town at 10k further. Otherwise, I found plenty enough easily. As usual, before you leave an accommodation ask where the next one is. Forget guide books, ask the locals. I easily found many where the book says there isn't.
Was a great trip, recommend, took in their best culture and history and would like to do it again. But the road basically followed the Irrawaddy. I did it in December, the wet had just finished and they were remaking the roads. In the wet they flood and are impassable.
East from Mandalay didn't appeal to me. Too much scenery. People, and food, are generally more fun.
Also the east opened and closed by the day then. Probably still does. Depends on whether the drug lords are behaving themselves. When I was there it was mainly closed. Apparently they were disposing of not wanted people at about 5 a day. As those were mainly police, they didn't even want to go there.