The needle size in a pattern is a starting point, not a guarantee. Your swatch tells you whether that combination makes the stated gauge in your hands. If it does not, change needle size before changing the yarn.
Needle material affects how stitches move. Smooth metal can suit a knitter who wants less friction; wood or bamboo can offer more grip with slippery yarns. Cable length matters too: choose a circumference that lets the stitches rest comfortably without stretching the fabric.
Use the needle that helps you make the fabric you want, then record the result with your project notes.
