What if my iPhone the only device I currently have? Should I be using a recovery key in the event that I lose any data?

There is no "recovery key". Back up to iCloud, so you can restore the data on your phone if need be.

How to back up your iPhone, iPad, and iPod touch with iCloudOfficial Apple Support › en-us

A recovery PIN protects your Apple ID, not your phone. There are pros and cons to a recovery key.

Recovery Key Approach

Pro: If you forget your Apple ID password you can reset the password using the recovery key immediately

Con: You take complete responsibility for managing your Apple ID and its password; if you lose or forget your recovery key you will never be able to use your Apple ID again, or unlock Activation Lock on your phone, rendering it useless.

No Recovery Key Approach

Pro: If you do NOT have a recovery key and you forget your Apple ID password, Apple will help you recover your account; see→How to use account recovery when you can’t reset your Apple ID password - Apple Support

Con: Account recovery can take days or weeks for Apple to process your request for recovery