A common choice is to use knobs for all drawers and pulls for all doors (or vice versa). The problem with knobs is they are harder to grip and fingernails tend to mar the cabinet door. It is much more comfortable to open a drawer using a pull, which allows the whole hand to grab instead of only your fingertips. We generally use pulls (no nobs whatsoever) in our kitchen designs.
Let’s talk first about metals. As a general rule, I like to keep the different metals in a kitchen to no more than two. If you have stainless steel appliances, that counts as one metal. So that leaves one other metal you can bring into a kitchen. If you’ve got brass light fixtures, that’s your one other metal. Your new hardware should be nickel or brass.