>>376926for a touring offroad motorycle you wil want to look into the 650 dual sports
DR650
klr650
and the XR650
these will handle highway speeds while still making offroad doable
They also tend to be quite cheap (you should be able to find one in decent shape for 3k depending on where you live
though you can make most motorcycles work with enough persistence
as for a backpack it probably wont be enough carying space plus riding with a backpack on can suck ass
if you do get one find something with chest straps
