Elias here with Shopify Support. Thank you for reaching out.
I understand you're looking for some suggestions on design apps and whether they're recommended. Just to clarify, are you looking for an app to help design a the storefront (eg. custom landing page)?
If so, you can consider using a third-party page builder app, such as Shogun Landing Page Builder or PageFly Landing Page Builder. Though page builders do allow you to build a more unique landing page; however, it's not something that I think every shop needs, as the native Storefront editor is capable of doing many of the elements. It's also worth noting that while there are benefits to using a page builder, such as being able to drag-and-drop elements on your pages, but you may also work with a bit of coding. I'd recommend trying both the Storefront editor as well as a page builder and seeing which one you prefer.
If you need any help with these apps, the app developers are always available to assist you. You can reach out to the developers directly or check out their guides and resources through the contact information found in the Support Section of their app pages.
Let me know if this is what you're looking for?