I did the LFS build with SysV init scripts. I think there is a systemd version of LFS. LFS was a good learning exercise to see generally how everything was put together. I wouldn't want to manually manage all of this myself.

If you look at the LFS compile instructions for each package they are essentially the same as the PKGBUILDs scripts in Arch, I suspect it is similar with Gentoo, Void or any other similar Linux distro.