WPtouch is one of the best mobile WordPress plugins around. We use it on many of our websites to make them mobile-friendly. While WPtouch works well for the most part, the plugins that you have installed may not be fully compatible with it. In our case, we had a tough time getting Sharebar to work with it. Its social sharing buttons were simply breaking our mobile theme. Regardless of which plugin is causing your mobile site issues, you can easily disable it from the Core Settings Page of WPtouch.
Should you disable all plugins? Probably not. You can seriously break your website if certain plugins are absolutely necessary for your site to function properly on mobile devices. In our case, disabling ShareBar has fixed the issues we were experiencing with WPtouch. Keep in mind you can force WPtouch to ignore certain pages and define custom user agents on the same page.
Disabling plugins may or may not make your site run faster and more smoothly on mobile devices. It is certainly a nice option to have.