If you plan to relock the bootloader after the installlation
this is not mandatoty, and only available with Official version, why relocking ?
Most important thing to take care about is the “android Security Update" aka "Security Patch Level” date (SPL) included in the installed Operating System on your device at time of the unlock.
new version on witch you want to relock the bootloader, must included a NEWER (or the same) “android Security Update" aka "Security Patch Level” date (SPL),
otherwise you risk to change your device into Brick