I am going to answer my own question.
I finally did it!
Here's how:
- change desktop resolution to 640x480@70Hz
- copy dgVoodooCpl.exe and its DDraw.dll to the folder of Jazz2.exe
- run dgVoodooCpl.exe
- switch to DirectX tab and under Resolution enter 640x480
- click OK
- run Jazz2.exe
Enjoy butter smooth scrolling!
It also works with 800x600@70Hz that JJ2+ supports!

You have no idea how happy I am.
I'm going to play all of the episodes now.