Is there a way to put parameters around what attachment does or does not integrate back into Smartsheet?
At the moment there's no way to limit which documents will be attached to the sheet after they are completed. I'd encourage you to submit an Enhancement Request for this feature.
Keep in mind that Smartsheet Labs integration are not officially supported so we can't make any guarantees about feature requests.
Do you know if there is way to share workflows in Smartsheet Lab with other users of the sheet and same DocuSign account?