Samsung locks the bootloader, even for carrier unlocked versions traight from samsung's website. (At least for those sold in the US, not sure about other places)

If you don't intend to use a custom RON like Lineage OS, you wouldn't notice a difference. But if you do, then it might be a dealbreaker. As for the Xcover series in particularx the specs are worse for the amount you're paying. Camera is worse, SoC is slower, assuming if you are conparing the price of a brand new mainstream S or A series phones to a brand new Xcover series. But if you don't care about worse specs for the swappable battery, then sure, go ahead. I personally wouldn't get the Xcover series, doesn't seem like a good deal, the screen is LCD and I'm way too used to OLED/AMOLED of the more mainstream phones.