PKVT, like said in earlier posts are mostly VTs or long finned PKs - I researched it a bit myself. A lot of the tails were almost like Round Tails.
As for paterns, I think marble patterns are dominant, but may not show up until later in life. The betta colors may change as they get older - or even well after you think they're past that age. Marbles are unpredictable. I HAVE had experience with them. Some people are pleased with the changes, but others find it unfavorable.
I personally like it, but there are still some in the fry who may not get it. There's just no way to know until they've lived out their life. But all will be carriers.