I’m not sure what you mean about sub-taxonomies. Are you referring to the actual term? If so you could use the following to template it:
taxonomy-$taxonomy-$term.php
An example of this would be if I had a taxonomy called genres and a term called horror, I could then template this as:
taxonomy-genres-horror.php
Refer to the template hierarchy for more:
https://developer.wordpress.org/themes/template-files-section/taxonomy-templates/