Smoother treble sounds right (though my wife did more back and forth) between those 2 more ... I might describe it as a peak in the treble for the V6S that hurts her ears. It is not noticeable for her on for example the 8.A's which has smooth treble.
Whether her comfort was due more to the tuning of the treble or adel, can't say right now.
It is closer to the V6S than the V8 to my ears ... But no is not a take on the V6S, sort of like the clarity of the V6S, soundstage of the 8.A, as well as some of the 8.A (not V8) sweetness, with more openness and ease than any of those.
Last 3 points totally yes and totally due to Adel, the bass is not as thick as the V8 or 8.A, but if you listen for a while you realize that what is really missing is the stuffiness of the bass, it feels like it is going all around the room not all shoved into your head.
Due to that if you are coming from something like the 8.A or V8 takes a bit to adjust ... Though I find the 8.A surprisingly easy to switch to and from as they are both spacious and somehow the 8.A's bass is not too stifling but again A12 is more natural ... Not neutral as in tuning I.e. not as in "leaner more detailed aka less bass" but with Adel and the large stoundstage it sounds or rather feels how it should and that is Adel!
If in love with a V8 you might miss the intamicy of it, I like big soundstage so for me the 8.A is far preferred to the V8 and thus the A12 is a fantastic experience ... If you want really thick explosive pounding your eardrum bass right in your head the large headstage and lack of pressure in your ear will defiantly take an adjustment period.
I will say V6S, VS and A12 are clearly all from 1964 and share a very detailed clean sound ... If you have listened to other V series already you will have a good idea of the basic flavor... Just make it much more spacious effortless, realistic especially to bass and easy in your eardrum and you will have a very good idea of the A12.
On mobile I will check for typos later.