This seems to differ by brand quite a bit and i have no clue why one is labeled one way vs the other.
Kevins Flo inks are less opaque in my experience than his neons when printed through the same mesh, but the tones are deeper in a way, though appear kind of washed out without a p/f/p or super low mesh AND a p/f/p UB. they are also super sticky. The neons are more of a bright tone (due to the white i assume) but are much more opaque. I print the neons just like I would any other ink and it prints great and looks great. I hate the flo's personally, but still need them for the right color on certain jobs.
Triangle's flo's are similar to kevins (deep tone, but sticky, require p/f/p base and low mesh for opacity), and I have not tried a comparable neon (do they even offer neon vs flo?)
One stroke has a bunch of flo's that act more like kevin's neons, opaque and brighter vs deeper tone. I think they also have neon, but again I have not compared.