Telegraf is, so far, a purely experimental addition. It shouldn’t be running by default even—thanks for the find!
It was added by request from a specific user who wanted to test it. So far there’s no automatic config management for it, so it’s indeed safe to configure by hand. The config will survive reboots, though not image upgrades.
We are planning to make a CLI for it, but we aren’t active Telegraf users, so we’d like to hear from its fans what options they want to see there. If you have CLI design ideas, please share!