So there is a thread on quieting things down in the Passat on Vortex (sorry don't mean to cross post). General consensus, rear trunk and wheel well area is a source for road noise and minor squeak. Front A pillars wind noise, and roof loud on heavy rains. Most bang for the buck is some insulation in trunk and rear wheel wells. optional on A pillars and roof. Doors help but not before the rear is done. I have a 2017 SEL Premium, and I find for around the Seattle area with rough paved roads (I-90 East bound) and local highways with stock Conti's it can get pretty loud. 3M spray on dampening coating in the wheel wells also helps. I'm planning to do trunk and roof then doors on my car.
You can go all out, like some folks did, but the biggest bang for the buck are those areas. If you want to sacrifice a little grip look for the touring tires with low resistance compound. I did that on my mini-van and it made a HUGE difference, but due to softer sidewalls typical of these tires, and the compounds used, it made the van feel less controlled albeit I actually gained wet grip (more to do with tread pattern and siping) with minimal loss of summer grip.