shopify mobile theme/UX + shipping question

hi guys
i am adding my shopify store into an all mobile experience in an app creator site, problem is since its embedded most themes looks kinda awful

so my question is, where can i find the best mobile (even if mobile only since i dont need the website) themes for spotify ?

another question, if i want to add multiple custom local areas each with its own shipping rate, what plugin can help with that ?

with regards