On mobile browsers, the font size is capped to prevent excessive sizes. Therefore if you increase the size of the bar past a certain point, it will impact desktop only. However, if a bar only targets mobile only, the cap will not apply.
There is a way to make the mobile font substantially larger and still target desktops too, but this requires activating two bars simultaneously (a Premium feature). To achieve this, create two bars:
- One targets the desktop devices
- One targets the mobile devices
Using this technique, the mobile bar can have a larger or smaller font size.