The factory Pitch Circle Diameter (PCD) of a Mk2 Golf is 4x100 meaning 4 holes 100mm apart (at their centres).
This was the same across all models for the entire production run. If your car has anything other then 4x100 then it's due to a conversion.
A popular modification, which often goes hand in hand with a more powerful engine conversion is to fit 5x100 hubs from a later VW. This is usually done so the running gear can also be taken from the donor vehicle. Although changing the ends of the driveshafts will allow you to keep 4x100 hubs if that's your preference.
5x100 provides a difference selection of wheels and brake set up.
More info on PCD:
The PCD is the diameter of the circle which passes through the centre of all the studs, wheel bolts or wheel rim holes.
The easiest way calculate the PCD is as follows:
1) Measure the distance ‘S’ between two adjacent studs from the centre of each hole.
2) Calculate from the formula below
**Note: on 4 lug fitments you can measure from the center of one stud to the center of the stud directly opposite.
PCD Calculation Formula
4 Stud PCD = S / 0.7071
5 Stud PCD = S / 0.5278
6 Stud PCD = S / 0.5
Credit Konig Wheels (https://konigwheels.com/wheel-info-tech/what-is-pcd/#:~:text=The%20Pitch%20Circle%20Diameter%20(PCD,the%20centre%20of%20each%20hole.)