You could decide to go toward china in the mountains, however the difficulty and the distances soon become a problem.
Mandalay – Pyin Oo Lwin: 70km with a big climb, nice road and nice surface. There is a lot
of traffic but not much dust (relatively:).
Pyin Oo Lwin – Kyaume: 110km. Very challenging I think, one serious climb on
the way. I saw cyclists doing it but didn’t manage to speak with them
afterwards to know if they regretted or not. Total ascent of 1200m. Pleasant road all the way.
Kyaume – Hsipaw: 35km nice and sweet
Going past Hsipaw is not really possible as the distances are too big and you are entering serious mountains.