20runs the gamut. Mostly two lane opening up tp four in places. Rt. 20 is the main street for many many towns across NY. Expect rural driving interspersed with commercial districts.
Certainly not a drive if you do not want to sight see,a wonderful drive if you want to smell the roses and take it easy
I-90 parallels and not a horrible distance away if you need to escape the slow drive.
Syracuse and Rochester are the largest cities but you can get around the downtown areas with a little map work.
Every fifteen or twenty miles will be a small village that will have you at 30 MPH.
you will want not to be on 20 into Albany, downtown in to all the state offices, congested and stupid.