I created a Web app and now converted this to a Cordova App. When I deploy it to my Windows Phone 8.1 device, the text is extremely small, much smaller than in the browser on the same device. I now created a mini app which just shows one line of text, same here, text is small in the Cordova App, text has normal size if I run it in the Browser on the same phone.
I tried creating it as Windows Phone 8 App, then the text has the right size.
I played around with the viewport meta tag, didn't change anything.