I've never had the Dekang RY4, as I've done DIY from the start, and haven't seen any concentrated flavorings by them.
My impression if the RY4 - Double is favorable. It's the best
tobacco flavoring that I've had so far, though there are still many flavorings that I have not tried. It has a bit of sweetness, but I add EM or TPA
tobacco Blend to further sweeten it, as I like my sweets. I also often add a hint of something else. I think of it as my pipe tobacco base flavoring.
Last week, I was doing peach tobacco, this week, I'm doing cherry tobacco. I think that it goes quite well with a bit of their Bavarian Cream flavoring.