Registering your SQL Servers participating in availability groups by the replica node name is the preferred method for the following reasons:

• You can perform backups and recovery on all databases of the registered replica node.
• Your backups are performed based on the availability group properties' backup preferences.

Keep in mind:

• Each replica node needs to be licensed.
• All nodes in the availability group can have the backup agent installed using the bulk agent installation wizard.
• On nodes where the agent should not perform a backup, SQL Safe automatically checks the backup preference and either performs the operation or skips it. 
• Enable jobs on all nodes at all times to prevent a failover event.