Yup, so no need to overcomplicate the lore now. I will probably post another revelation/confirmation once I feel like it, but given it's still March, it too will be within spoilers.
So, it's confirmed in-game that yes, the enemy Octolings are in fact, the older versions of the playable female Octolings, as seen from the image below of female Octolings that have the eye markings and eyebrows of the playable variant, but the hairstyle enemy variant:

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