Miller has been on a Honda recently so we know that he likes the Ducati better; Dovi has ridden all those bikes with good results in the circumstances, and even if it was years ago I think he could still be competitive on all. Petrucci... yes, he should probably stick to Ducati. Or perhaps KTM in 2020-21.
Yes, and Rabat too.
Dovi was very good on the Yamaha and Honda, but he was never battling for championships or taking six wins a season. I doubt his 2017 would have been so strong on a Honda or Yamaha.