I would say, even getting CSE is also not a very tough job. If you have prepared for JEE Mains well, then COMEDk is a cakewalk. Questions in COMEDk are quite direct. NCERTs are the best books to refer for COMEDk I would say. Especially for Chemistry. And yes, they give one hour for solving Maths portion. So you got to be quick with your calculations. Mathematics section creates most of the difference in final scores.
I myself didn’t prepare for COMEDk, but I did prepare for JEE Mains.
Average cut off over the past years for ECE is 900 I suppose, and that for CSE is 450 or so.
So for Chemistry: complete the NCERT.
For Physics and Maths, just get ur concepts clear, questions are gonna be easy.
All the very best! : )