I don't know very much about all the different brands. There are so many like you said. I just know the experts say http://www.plasmafire.com has the best. So I bought that one.
Ozonated water can cure candida. I would also say H2O2 (Hydrogen-Peroxid) would too. I've been spraying it on the body after a shower for a few months now and have become a firm believer.
You don't need a meter to tell how strong the water is. Just go by taste. You can't get too much in a glass. From what I've been told you can only get about 6% max. in a glass. I've experimented and found for me, 20 minutes is the best time for the two generators I have. Just if you feel bad after drinking some slack off on the concentration, or frequency till you feel better and build up slower from there. Once you get used to it, you can drink a lot.