Each metadata source can be configured to which of the site
available metadata to use.
If you remove the tick from Tags on all OTHERS, only GR will supply tags.
Cover Metadata has a Preference number that can be set. The site that gives me my preferred cover gets a 1, the site that always returns
too small covers gets a 5

it is better to leave fallback sources. If a site goes down (or changes), you get nothing.