1, They are not carts (that is what is causing the confusion). Some 2-piece e-cig companies like Vapor4Life call them carts/cartridges but they are actually cartomizers (the combined mouthpiece+juice+atomizer of a 2-piece ecig). We call them cartomizers or cartos.
2. Vapor4life is a bit confusing
Blanks - WOW Carts are somewhat lower resistance and hotter, Coolcarts are somewhat higher resistance and cooler (by resistance I mean electrical ohms, nothing to do with how they drag)
Prefilled cartos - WOW prefills have WOW juice in them. It doesn't not mean they are WOW blanks. Some are and I think some are not. Premium prefills do not have WOW juice in them - they have the other juices. Again, I think some may be in Coolcarts and some may be in WOW carts. So far I prefer the WOW juices though the Premium/Nobacco juices may have more TH. My guess is the WOW juices might have more VG and a bit extra flavor?
Buy one of their drip tips. If you get a carto that is hot on your lips, use the drip it on it as a mouthpiece. Alternately you can cut a small circle out of the middle of the round end of a carto condom, cut the length a bit, and use it as a cover for
vaping a hot carto.
Or find some soft-cap KR808D-1 blanks you like elsewhere and fill them yourself.