My clients always ask me about this. This is a great resource that has most of the options in one place. 
What is the difference between the Iconic plugin elements and the normal relative element? For example the Iconic Icon, what is the difference compared to just using the built in font awesome Icon as it relates to operability on a mobile device?
I have wondered this too!
Good question – Ionic elements are configured with small differences that cater to mobile-specific events and improve the mobile UI/UX of your app. For instance, sliding open an element is an action you’d use on your phone, rather than desktop, and Ionic has already incorporated that logic into their elements. Another (outdated) example is that in the past, mobile elements used to have a 300ms delay after you tapped on them; if you used a regular Font Awesome icon, it wouldn’t have that delay while Ionic elements would’ve integrated that delay. In sum, there are very small differences between the two icon types, but using Ionic elements can help ensure that using your app on a mobile device feels “normal.” Hope this clears it up a bit!