Regarding playing sfx in cutscenes I think the easy way would be to have a cutscene node with script with function for each needed sound. Using the animation player node you can animate as well functions - adding sounds even to animations :).
Regarding the course - please, don't feel offended I completely didn't have anything negative in mind. I too drew a lot of inspiration from it and used (as allowed by the game jam) some general code like platform movement with major modifications: https://heartbeast-gamedev-school.teachable.com/courses - if you haven't used the course, I really recommend it - probably best game dev courses I have seen.
