If it's print OD, you're in a great position for low cost testing - just fire up a few designs and run some Google Ads + maybe a little FB traffic straight to the product pages and see how they convert.
That data will give you a better answer than opinions 😄
I personally like the niche (and youtube videos!), but haven't tested so I don't know how it would perform.
Peoples pay 30% more for personalized product and it is a growing market in almost the majority of the categories.
See mediaclip.myshopify.com to see our Shopify plug-in for print on demand. Don't be stuck with only one suppliers that the key to your success.