Yeah for my case it was easier in the initrd otherwise I’d be trying to roll back the active / partition.
Re run levels, they were a sysvinit thing so I wasn’t sure sure about systemd, this suggests that would work though https://fedoraproject.org/wiki/SysVinit_to_Systemd_Cheatsheet
And if you have to bail out even earlier, run level 1 will give you the rescue.target
You can also use
systemctl status $pid
to find out what service a process is from.