The previews on how the responsive email templates from the library work are to be found here:
http://templates.marketo.com/category/responsive-email/
Here you can switch preview to a smartphone view to see how it reacts.
Those are all 1 template, if you import them and create an email it should look good on all (mobile) clients.
You don't have to create to emails and tie them together.
If the Marketo templates work correctyl I can't say, it's also about what content you place in the template maybe. I don't know, I think support could help you with that question.
If you want to easily test template you could use litmus, if you test an email here you see all relevant screenshots, example:
https://litmus.com/pub/c41539d/screenshots.
I hope this anwser your questions and helps you, good luck!