Subthemes are basically more specific versions of the themes. Check out an example on our Twitch demo: https://demo-twitch.getthematic.com/#!/demo/main/dashboard/2... You will see a base theme "use chat", with subthemes like "chat in landscape mode", "chat on a tablet", "type in chat" etc. Does this help?

Thank you so much for the offer of introductions. Definitely interested, as we sell internationally, not just in the US.