Theme don’t delete or disrupt anything adding in Custom CSS or other customizer option while updating or upgrading from free to pro.
Also while upgrading from free to pro, you just need to adjust some of the widget setting only, other setting are automatically migrated including Custom CSS.
The main advantage of using SuperMagPro is there available more setting and controls in the theme, 12+ custom widgets( Free only 2), Video Support, Advanced Related Post options etc, We will list soon and keep them in our website :).
A lot of the features different you can see in the demo too:
SuperMagPro Demo : https://demo.acmethemes.com/supermagpro/
SuperMag Demo : https://demo.acmethemes.com/supermag/
also definitely we provide more priority support for our premium theme user.
You can buy SuperMagPro theme from here http://www.acmethemes.com/themes/supermagpro/
If you have further any queries please feel free to ask.
Best Regards,
AcmeThemes