What DNS records are updated periodically?

I’m looking into moving my DNS elsewhere using the information on the “External DNS” page.

I’m wondering if there are any records that are automatically updated (such as the domainkey), or are those all static?

The DNSSEC keys as part of nsd are automatically rolled over / renewed as necessary. So you’d need to ensure this as well if you used External DNS (if you wanted DNSSEC kept running that is).