Blank = the mesh key. Your keys are sent only to nous.api over HTTPS, never stored server-side. (Saved in this browser only, in localStorage — plaintext on this machine.)
The Vertex Model Garden, mirrored here — browse it without leaving nous.api. Green models work today through the gcp-bridge. Amber models need a one-time terms acceptance in YOUR GCP project — accept there, hit Refresh from Google, and they appear in the provider picker above automatically.