May one prep Limudei Kodesh teaching on Chol Hamoed by typing on a computer but not printing till after Yom Tov?

It is best to avoid school preparation even for Limudei Kodesh if it is arduous work. Arduous work is only to be allowed when there is a need for the Chag itself, or דבר האבד. Since it can be done after the Chag, it would be preferred.

See the Mishna Berurah 530:1 towards the end in the name of the Yerushalmi that the purpose of Chol Hamoed is to learn Torah, so if this work is like “learning Torah” more than “arduous work” there would be room to be lenient.

Similarly, if your work involves your creativity, there is room to allow Torah creativity. However, if you are doing work which is more “technical preparation and without your creativity” it should be avoided.(Sdei Chemed Maareches חול המועד סי’ יא בשם שו”ת לב חיים)