Sachs used to be the old supplier for VW back in the mk5 era but now they are using Monroe. I have not had any experience with Sachs myself but I've recently fitted Monroe all around my old car. I've had KYB previously and the shocks might as have been welded stiff. If you want comfort, stay away from those. My other car on Bilstein b4 sport, Eibach pro-kit and 18" wheels was more comfortable than the KYB shocks on stock coils and 16" wheels. Monroe on the other hand, I instantly felt the difference, especially going over speed bumps.
If you want comfort, go with either Sachs or Monroe.
As for the dust covers and upper mounts, for the rear doesn't really matter what you pick, just check whether your mounts are oval or round. Not sure what the exact difference is between the 2. Maybe just something VW changed over the years? They are interchangeable but I'd assume the oval ones provide much more bottom out damping force as they are wider.