Can i delete macintosh hd data after downgrading from catalina to high sierra

I recently had to downgrade my os from catalina to high sierra to fix my computers performance issues

I was able to restore a good chunk of my old user data from my time machine back up but i noticed that my memory was doubled compared to before i started this project

Thats when i found put that catalina does mac hd data for security purposes. My understanding is that i somewhat have double of most of the files

I wanted to know if its safe for me to delete macintosh hd data without issues? And how would i go about doing that?