What RHR is a fairly good indicator of is how rested you are, so if you monitor it you can learn how well your body is adapting to the training load you are putting it through.
I prefer to monitor sleep quality and time.
But my sleep isn't interubpted by kids or other stuff. And I go to bed between 9-10pm and get up to 9h a night. I know how rested/tired I am by how I feel.
I prefer to measure things of my own perception and intuition.
Maybe I should have added a 'other measures are available' disclaimer. Monitoring sleep is clearly beneficial too. Basically find something that works for you and keep an eye on it.
What RHR is a fairly good indicator of is how rested you are, so if you monitor it you can learn how well your body is adapting to the training load you are putting it through.