Hello,
You can not change the product page design category wise, the same template applied on all the single product pages which you have chosen from Theme Settings >> Product Page >> Product page design. Only the inner content changes according to products but the layouts still remain the same.
But if you want different page design on different product pages then edit your those specific products and go to “PRODUCT DESIGN & COLOR OPTIONS” from the “Product page design” select some other option except of “Inherit” and update the product.
Screenshot for clarification: https://jmp.sh/Keoo0L6
Best Regards.
.
