This is different thing. If you not technically minded, then don't do it. Yes updates are for different regions, carriers, models. This is why phones ending with different letter or number. SM-S928*
*B, N, U/U1, W, 0 etc.
For an example OXM in firmware - includes Multi CSC.
Unlock Bootloader doesn't void warranty. But to root, install custom firmware voids warranty.
Samsung Galaxy Note 20 Ultra