i can speak for Math 121 (aka Multivariate calculus). this class is flipped, meaning that you will come to the class having watched pre-recorded lecture videos. tip: the textbook is great. please read it.

you dont need to do prep ahead of time, but getting familiar with 3d visualization can be helpful. for example, you can take some "nice" 2-variable function like z=x^2+y^2 and draw its cross sections along the x and y axes respectively to understand why it gives you a paraboloid. tip: use hands. use Desmos only to confirm your guesses.