The 600Hz marketing malarkey refers to the temporal dithering speed plasmas use to produce gradations of light and color. Its related to refresh rate in a sense, but not in a way that's a useful in comparison to LCD refresh rate.
"24p" is more or less a format/signal standard that refers to blu-ray players' ability to output 1920x1080 at 24Hz. The B450 no doubt "supports" 24p in the sense that it will accept the signal, but it will always do 3:2 pulldown (if it recognizes film cadence properly) and display the source at 60Hz.
Not to be rude, but it would serve you well to do some searches and basic reading of prior posts. There is a ton of information on this stuff here on the forum and elsewhere online. 600Hz is mostly marketing crap. 24p is mostly marketing crap, except when fully supported by all your gear.
If you feel you need 3:3 (72Hz) or 5:5 (120Hz) pulldown, there are plenty of sets out there that will do that. AFAIK, no plasmas do 120Hz at this point, but 72Hz is plenty and the Automotion Plus and similar technologies that LCDs employ to interpolate frames is also a bit of a gimmick, in my opinion.
Also, I would recommend you stay away from plasmas that do 2:2 pulldown and display film sources at 48Hz (only the Panasonic G10 series does this, that I'm aware of). I have not seen an implementation of this that didn't produce flickering due to the low refresh rate.
A final note, some forum members have stated that all the 2009 Panasonics employ a low-level frame interpolation scheme. I can't confirm or deny this, but if true, I believe it might reduce film judder to a degree, even at 60Hz. Would anyone care to chime in if you're in the know on this topic?