No hostility intended or as far as I can see posted, just making sure it is understood KaOS is not Arch. Far too many are confused about what KaOS is, install it thinking it is an easy way to get Arch, then being disappointed it is not. Same for using the manual option to install, there are no defaults for manual, user can do all kinds. And as pointed out, to use Btrfs, some understanding how to use it will be needed. But that is the same for using EFI manual, or GPT on BIOS. All those will fail if not doing some steps correctly.
This thread will not be deleted since it does contain some valuable info for anyone wanting to learn options to install with Btrfs.