just a couple notes! not comprehensive.
once alpine linux has boot, login with 'root'
then, control what the installed disk will look like by using some env vars.
setup-disk script
$ export SWAP_SIZE=0
$ export BOOT_SIZE=1024
$ export ROOTFS=btrfs
$ setup-alpine
& step through each step of the installer.
when the installer asks about disks,
select crypt > sys for a luks passphrase encrypted system.
setup-alpine script.