So I’d like to know what the difference is between placing the bootloader on the MBR when installing and chosing encryption and placing it in the system partition (/). I couldn’t find a documentation about this or maybe I’m just blind.
What’s the best option when not dual booting and only using EndeavourOS?
Unless you hardware is very, very old you should be doing a UEFI installation which would boot using an EFI partition. If you use full disk encryption, the EFI partition would not be encrypted but the kernel and initramfs would both be on the encrypted partition.