Can we roll back system files w/o brick? topic

Got a simple question can we roll back from say SU5.24 to SU4.21 using a prior TWRP backup?

I know we can not downgrade the gpt and tz but can we roll back the system files? Of course deleting or freezing the OTA file to prevent an ota update? Would think that it would only be an issue of the newer Bootloader working with the older system files.

This is my daily driver so don't want to test prior to some input from those who have that experience.

Thanks ;)