For the record, there is a way to get back to the state of the OS before the update without a factory reset …
But now that you did a factory reset, the TWRP restore should be the way to go, see my earlier post on how to do this.
What about your data in Internal Storage? Since TWRP excludes this from backups (there’s a message about this displayed while backing up), do you have a copy of this? Or do you sync everything to the internet?
https://twrp.me/faq/backupexclusions.html