Hello, does anyone know, does these two share the same radar and software for the ACC? 

 

I felt like Passat acc was a bit smoother in city than skoda superb. 

 

Adaptive cruise control. 

Depends on year - but for the most part, yes. 

 

They will use either 3Q0 or 2Q0 radars with very similar, if not identical datasets.

The drive mode setting affects smoothness of ACC.

may not apply in the OPs case but my MY18 SE almost poverty spec MK3 doesn't have the drive mode options. What it does have under car settings is a separate ACC menu where you can tell it which mode to use. No idea if cars with Mode selectors have this same setting.