It's not possible to know how a third party extension will work on mobile.

Using Responsivizer you have a shell that is fully Responsive and optimized for mobile, but if inside that you are running an extension that is not mobile friendly or not mobile compatible, results are not predictable.

In some cases Responsivizer is able to correct part of the extension layout that are not responsive, in some other cases some CSS adjustments are required.

However notice that Responsivizer is able to deal only with layout and styles, this means that if you have an extension based on non-mobile technologies such as Adobe Flash, Silverlight, etc nothing can be done to make it work on mobile devices. In this case you need to replace that extension with a most modern one based on HTML5 standards and working on mobile devices.

Often it's a good idea trying to ask to the extension developer for un update that is compatible with mobile devices. All Joomla developers should be aware that the extensions they release should work fine on mobile.
In particular nowadays Flash based extensions are not compatible with mobile devices, Apple refused to integrate Adobe Flash support into devices such IPhone, IPad, etc and Android has only in some cases some chances to get Flash player installed following complex configurations.