Shampoos aren't usually designed to "strip" anything, which is why we use car specific shampoos and not Dawn dishwashing soap. Not only are car wash shampoos safe(r) for paint finishes, but a lot of them have added chemicals to help *preserve* paint finishes and protectants.
That being said, the method in which you wash your car will have more of an impact on how much lsp is removed vs. what type of shampoo you are using. Always be as gentle as possible and mix the shampoo as directed, never stronger, and in some rare cases you can even mix it a little weaker.
I find NXT wash a *decent* wash. It cleans well, but lacks a little in the lubricitiy dept. For the price, and the fact that you can find it just about anywhere, it's not a bad choice.