Hi Danny and welcome to the forum
In regards to keeping up with price changes, you really need to be working with a good Dropshipper, a supplier that gives you advanced warning of upcoming price changes, such as specials or price increases. If you don't have a supplier doing that for you, then that could make your life pretty difficult. So that's something you really need to discuss with the suppliers themselves.
In regards to your suppliers charging different shipping rates, do you mean on the same items as each other?