I know you asked for cli apps, and maybe you have already heard of it, but in case you haven’t, cockpit is a pretty nice web UI for managing your server (not just systemd services, but everything)

I think that systemd oomd is pretty slow. I get a quite a few minutes of unresponsive system while waiting for oomd to do something. Honestly rebooting is faster than waiting for it to work.

I recently installed and enabled earlyoomd on fedora, and on an initial test, I still got an unresponsive system with the default settings, but after around 20 seconds or so, it killed the responsible process and I was able to continue working. Not perfect, but much better.