The consent default command sets the initial consent state for Google's tags before any user interaction, scoped per region if needed. It accepts the six Consent Mode parameters (ad_storage, analytics_storage, ad_user_data, ad_personalization, functionality_storage, security_storage) and should run as early as possible, before any tag fires that sends data.
The consent update command tells Google's tags that a user's consent state has changed, typically after a visitor interacts with a cookie banner. It overwrites the values set by consent default for the rest of the session, but unlike default, it cannot be scoped by region.
wait_for_update is a gtag.js parameter that delays data collection until consent state has been resolved. It accepts a positive integer in milliseconds, typically between 500 and 2000, and is set inside the consent default command.