At our old VW Touran the lowering only with springs is absolutely ok, but forget lowering with springs or cheap coilovers at a VW T6 or T5 .....payed a lot of money for bad results and experiences at our T5 in the past.
Do nothing or do it right.
The one and only ...what really works plus superb handling and ride comfort : Bilstein B14 PSS coiloverkit