What sound the pros and cons for using Modal? Whereas the webapp is responsive and will be displayed on mobiles.
It's a UI tool like any other. Sometimes you need to get extra information on some action and want to stop the user from continuing until you get the answer.
However, that doesn't mean you need to display it like a rectangle with a masked background. You could take the full screen real estate or even something more dramatic.
For example: Go here: http://tympanus.net/Development/PerspectivePageViewNavigation/index3.html
Click Rotate Left and then click Show Menu. Imagine your "modal" information was in that area that appears.
Modals have the danger of "inception". A modal on top of a modal on top of a modal. You need to be careful when using them to avoid this.
So, in summary, use it when appropriate. Avoid it when it's unnecessary. Keep them consistent in look and usage. Good Luck.