If I understand correctly, carrier locking is different from Bootloader locking. One implies freedom to use the device on any provider network, while the other is for installing a custom ROM. A Samsung flagship can be bought unlocked by paying full price, but you cannot unlock the bootloader and install Graphene, for instance.
The Exynos variants of Samsung devices can have their bootloader unlocked, it's the snapdragon ones that can't and even then there are some instances where it was possible to do it, but it's still a hassle and the Exynos variants tend not to have good development support.
Samsung has been good about that in the past. Motorola on the other hand I remember there being a bounty for the keys so they could run alternate roms.
Right but Samsung devices once you unlock the bootloader you loose Knox (which is pretty awesome IMO) and the only way to get it back is to replace the motherboard on the device... at least on my S23 ultra. As for the carrier lock, we'll once you finish paying for the phone you can unlock the phone right? Also, if you buy the phone from Google it's not carrier locked and you get the same finance options as the carriers