The problem is most likely the difference in PPI between mobile and PCs. As you probably know, the size of the text/sprites is measured in pixels. However, the number of pixels per inch is monstrously different between the two platforms, ie. my laptop computer has a resolution of 1280 x 800 on a 13" screen, while my Samsung Galaxy Tab S has 2560 x 1600 pixels on a 10.5" screen.
One solution would be to have an event "On Start of Layout" with the action HUDElement > Set Size (insert something like the device's PPI * the desired width in inches, & the same thing for the height) combined with the anchor behavior.
The device's PPI might be derived from an expression similar to "System.WindowWidth / System.OriginalWindowWidth".