I can tell you about the short sleeve and long sleeve button down shirts - Excellent quality! I have purchased a few for my son. I don't know about t-shirts; never bought any.
PayPal. It is the safest way to pay for any online purchase. However, I have used my CC on 10DollarMall's website a few times and did not have any issues.
Consult the size info near the photo... just to be on the safe side... call them and ask for measurements! If you are heavy set/obese their idea of one size... may not be yours! Hope this helps..