Ed, the Tender Quick and Sugar Cure are certainly different animals, compared to the #1 curing salt you ordered. The TQ and SC contain both sodium nitrites and sodium nitrates, in a much-reduced amount. The reason is that they are intended to be used as a dry cure. That is, rub them on the meat, put in a plastic bag, and place in the fridge. They require flipping daily, for several days (depending on what you are curing). The nitrates, in these, convert to nitrites, over time. Prague powder #2 is similar, minus the sugar.
The #1 Prague powder (also know as "Instacure #1) is a higher concentration of sodium nitrite and salt only. A little goes a long way! It is generally used for brines (wet cures), although it can also be used in dry brining.
I, too, have never seen Tender Quick in any local stores, but regularly see the Sugar Cure. I, personally, have never used either. I only do wet brine cures, so I haven't had the need for them. However, I am planning on trying some belly bacon (if I can just FIND some good pork bellies), so I'll be trying dry brining then!