Downgrade System Apps

Hello. I just installed MIUI in my MI MIX 3. Really liking it, but I realized from CustoMIUIzer that the rom doesn't come with the system apps updater. So I installed it and updated everything. But as consequence, lost a lot of the newer settings, and I can't downgrade them just by re-flashing the rom, as the apps stay in the latest version. What should I do? Already configured my phone and apps, so deleting /data and formatting everything ain't an option.

Thanks in advance