I never tried those tests from Red Sea.
What I can say is that API tests are a bit insensitive. I use them in the brackish tank only.
For ph, I found Salifert the best one due to range and distinguishable colours on the the chart.
The same goes for nitrate. Salifert can really distinguish between 0.2 and 1 ppm, e.g, and goes up to 100 ppm what should be enough.
For phosphates, I tried a lot, Salifert, API, Sera, and all are only good above 0.25 ppm, with Salifert the best, and API agan the most insensitive. Quite better but more expensive is the D-Deltec test (in cooperation with Merck) for 30 GBP here in the UK. (The real Merck test costs here 100 GBP).
Alkalinity, I tried even more tests but the all are quite good. Only watch out for the different units they are using. A conversion table is always in the instructions.