For my 2015 Golf TDI (not wagon) I ordered the airlift 80753 from Amazon. Worked great. I’ve had them on the car for about 6 months now and no complaints. One thing I would recommend however is to put a valve on the airline between the two bags. If you don’t, you’ll find that if you’re cornering the outside bag will compress and push air to the inside bag and cause even more body roll. With the valve it acts more as an anti-roll bar
I did T-them together but if you but a 1/4 turn valve on one side of the T, you can keep air from flowing across from one bag to the other. Just make sure you open the valve when changing pressure
Got a link to what this ¼-turn valve would look like for this small diameter line?
Seriously - folks have used the 80753 on many Mk4, Mk6 (which is where I first came across them), and Mk7, (and I'd be guessing Mk5...I just haven't noticed mention), so I don't think you'll go wrong with the 80753. Many users here have put them on all of those models and none of us have come back with complaints.
The size of the bag is more of a range. The bags are quite playable and need to be within .5-.75 of your springs measurements to actually fit…this is from what I’ve found