Just out of curiosity, what advantage will unlocking the bootloader give you if you're not going to flash a custom recovery or a custom ROM? You're planning to at least root the phone after unlocking bootloader right?
Unfortunately there is no known software method to restore Knox. It's linked to a hardware fuse. Even if you restore to stock, Samsung Pay, Samsung Pass etc will never work again. Some banking and streaming apps may still work if they're only looking for root and not Knox.