VW MEB platform owners should be able to chip in on vehicle specifics. I've not read about 12v problems on MEB platform, so far.
For HV Li-on battery, if sitting unused for a long time, it's generally best to keep Li-on charge level at around 50% if possible (at 3.7v per cell). Storing at 100% for days stresses the battery causing more degradation, same at 0%. Generally speaking storing Li-on battery between 30-80% will be fine.
I've no idea what VW manual will say for care of their battery. But Tesla manual differs to Nissan's.
Nissan: we offer "long life" mode to charge to 80%, no mention of long term storage. Leaf doesn't connect the HV battery unless the car is "started", so it will happily sit for months.
Tesla: set charge limit to "daily" (50-90%) and leave it plugged in. Tesla will use HV battery to top up 12v and heat/cool the battery to maintain temperature, so need external support if unused for many months.
The power rating of charge point will not matter. The important thing for modern EV is that it can draw from external source to maintain its charge levels. A well designed car knows what is best for itself.
I've parked up for 2 months on the Leaf without problem, at 50%, no % loss for charge level. For Tesla longest was 10 days not plugged in at a car park as we went on holiday in October. Dropped a few % on the HV battery. I think leaving it not plugged in up to 3 months is absolutely fine.