Ask IH: SquareSpace / Wix vs Custom Shop?

Hello! I am arriving to the point in my project where I need to start thinking about setting up a webpage. I've toyed with the idea of writing it from scratch, but I also know that it would be quite the undertaking to do so.

One reason I have considered writing it from scratch is our product is customized per purchase and I am worried that the SS / Wix experience might not be up to par. Along with this, I wonder if down the road, how easy it would be to leave a service like SquareSpace and migrate user data over to a custom shop.

On the other hand, while the experience might not be 100% at launch, the amount of upfront work is far less.

I feel like I am deep in analysis paralysis.

When is it the right time to create a custom shop for physical, custom goods and when is it best to offload the work on an existing service so you can focus on other parts of your business, in your opinion? Thanks!