I have my own test for floppiness. I take the brush and put pressure from the hair straight down on the palm of my hand. Depending on how crushable the hair is I know immediately if it's going to be floppy and how floppy it will be. I don't have to use it or wet it.
I don't think I've ever encountered a floppy brush that was prickly. That's a quality you usually find with the stiffer hairs.