Ive ran a shopify store last year and had no issues.
This year i went with the Redcap theme which i really like. ( MovingTshirts.com )
My product images are burry on mobile devices and its bothering me.
We all know first impression is everything.
I use printful and let the mockups push/sync to my store.
There should be no issue but there is...
I would hate to have to mockup each product separately and upload each . major time killer.
I just tried one of the Image optimization apps in shopify store but that hasn't helped any.