I think the size confusion you are running into is that the vinyl doll is smaller than the resin. In truth, they don't seem a lot different unless they are side by side. Both share clothing with Ellowyne quite well. I also have a handful of Delilah Noirs and all three mix well together in my opinion.
I think these are great dolls to play with. They have many of the features of the more expensive resin BJDs (changeable eyes, wigs, stringing) but at a price where you can actually experiment and play with your dolls without feeling like they should just sit on a shelf because they were so expensive.
Resin is fragile...my resin Evangeline has a small dent in her ankle because I twisted the elastic in her leg wrong...happened in an instant...Things happen but if you can't play what would be the point IMHO?
Hope you have fun with your new dolls.