Wind rang charts are on the net you should be able to find them there , go to ozone's web site should find it there , you should be able to download the manual for your kite as well.

dont bother on wind range that much. its all about being overpowered or not actually .
More concern about your weight - board. Your catalyst have different wind range from you than me . Now best way is to find the low end of the kites.

Get your 12 and test on how low wind (measure the knots on beach) you can kite and go upwind . then your 8m

you should use the 12 and when wind is like +2 knots of your 8 just change to that.

For sure dont try to find the high end of the catalyst and end up 2 overpowered and hurt yourself. At general you should be using your 12 from 10 to 18ish knots and then the 8m from 16 to 26. (pigtails changes apply on those ranges )

Consider on low end testing you may end up with your kite down and have to swim back (dont go 2 far away from shore when testing) and on high wind .. well get some more experience first to try out it as safe as possible