They more than likely all the same spring rate hence why they are for all mk3 golfs.
I would worry about it!
You don't worry about it when you got a passenger do you?
There isn't much difference in weight. It's just that where the weight is on a vr.
Not much difference in weight?
Have you picked a VR6 up?
I can lift a 6 cylinder block onto an engine stand...not so a VR6 block.
There is a HUGE difference in weight.
As for coilovers being the same...yeah, some are.
The trouble is, they ride really well in a VR6 where the engine weight works against the stiff springs...on the 4 cylinders they just feel too firm.
An example: Koni coilovers ride much better on the VR6 than the 16v...despite them being the same kit.