From what I see I believe you are over thinking it. You have an unlocked bootloader and TWRP installed, this is the hardest part. Now all you have to do is flash a stock Android 10 ROM and then follow THIS. If you follow it everything will be wiped (*DM Verity/Root files you have flashed) and then after you get /e/Q installed you can tackle the encryption through Trust in the settings (if the phone isn’t already encrypted, it will tell you, see below)
