I think altogether without explanation is best. Anything else would be another Worf "It is not spoken of with outsiders" thing that will only just open a new can of worms. Enterprise felt the need to elaborate upon it, which caused a bunch more head-scratching in some ways. A noble effort, but... no need to see history repeat itself.
An unspoken understanding that all variants and varieties exist in the same universe (I think) will be sufficient to make it work. The hardcore fans like us already know all the back-stories of the different species variants and the casual fans or non-fans will just shrug, realize that they're just another kind of humanoid alien and move on with the story.
The K.I.S.S. principle may easily apply here in this context.
An unspoken understanding that all variants and varieties exist in the same universe (I think) will be sufficient to make it work. The hardcore fans like us already know all the back-stories of the different species variants and the casual fans or non-fans will just shrug, realize that they're just another kind of humanoid alien and move on with the story.
The K.I.S.S. principle may easily apply here in this context.