Usually there is no problems with switching to another template. Just set the same template settings as you have in Mobile_Basic template, and disable AJAX navigation if it conflicts with other extensions. But sure we will assist you in the case of any related issue.
As to the speed, Mobile Joomla uses several optimizations to get higher performance (merging of js/css files, lazy image loading, image rescaling, AJAX navigation, etc.), but you use JCH Optimize plugin that does many of such optimizations on desktop version as well, so I do not expect there will be significant difference in loading time between desktop and mobile versions.