Just tried it out for a bit, and it looks great and is super snappy. It seems the CI portion is delivered by a project Woodpecker? How does this work and is compared to gitlab CI?

Forgejo has an integrated CI/CD solution, Forgejo Actions [1], that is very similar to GitHub Actions (and thus not so similar to GitLab CI). This is what you'll probably use if you self-host.

Codeberg (a public Forgejo-based forge) also offers Woodpecker CI. Their hosted Forgejo Actions is still in beta AFAIK, but you can also use your self-hosted runners.

[1] https://forgejo.org/docs/next/user/actions/quick-start/