That product you refer to is Dichlor. As for test strips, they are next to useless -- get a good test kit, either the TFTestkits TF-100 or the Taylor K-2006. The chlorine level you maintain is the Free Chlorine (FC), but you also see if the Combined Chlorine (CC) gets too high. Read
Using Chlorine in a Spa, especially towards the end of the post for a summary of the Dichlor-then-bleach method. You do not want to use Dichlor-only since that will build up too much CYA/stabilizer/conditioner over time. These are all synonyms for Cyanuric Acid and it makes chlorine less effective, but you want SOME in the water which you can get by using Dichlor initially because otherwise the chlorine will be too strong.