Disable Settings Sync entirely in CodeSpaces

Question

I manage a GitHub organization and would like to set up CodeSpaces so that organization members use consistent, predictable VSCode settings (at least when the CodeSpace starts up). I set settings directly in devcontainer.json. However, those settings are overridden by either default VSCode settings or settings that I had set on my local machine and that were synced. I disabled settings sync locally, but is it looks like CodeSpaces is still doing an initial sync upon creation.

Questions:

1. Is it possible to prevent CodeSpaces from syncing settings completely?
2. Is devcontainer.json the right way to set VSCode settings?

Thanks in advance!