Okay, I now got systemd-boot and refind working reasonably. Both have succeeded in booting from normal ext4 root and from btrfs subvolume root. Refind has been tested to work with encrypted root when ESP is mounted to /boot (therefore, no encrypted /boot). I also updated the bootloader descriptions a bit so user can make a more informed choice.
I updated the PKGBUILDs and made agithub release, so when @oberon or one of the other packagers has time to build it, it shall be available in the repos. This would be 0.8.11.