I'm using yootheme pro. Will your extension replace this on mobile only devices or completely? Also, do I need to buy a theme too? For a demo you say go to this site on a mobile device, I'm on an iPad mini and the site if anything is unwieldy, defy not for mobile. 

Usually we recommend to install Community version of Mobile Joomla and check how website looks on mobiles with Mobile Basic template (our extra templates use the same framework) and with default Joomla's template (Mobile Joomla may be used with default template too, in this case it will responsive for optional disabling of modules and plugins, image rescaling and lazy loading, and many other optimizations).