Should you dropship on Shopify or a marketplace?
A marketplace to find out whether it sells, your own store to keep the customer. The marketplace brings traffic and keeps the relationship; your own store brings nothing and keeps everything.
What decides it
The mistake is choosing one forever. Sell on the marketplace while you are learning what moves, and build the store in parallel so that when a line proves itself you have somewhere to take it that does not charge commission on every future order.
The part that gets skipped
The margin is thin by design, so the whole model depends on cheap traffic. When advertising gets more expensive, dropshipping stops working before anything else does.
A dropshipper who survives past the first year almost always stops dropshipping — they start holding stock for their best sellers, because that is where the margin is.
Returns are where the model is tested. If your supplier will not take a return, you are the returns department.
Where an app fits
An app is worth building once people buy from you a second time. Most dropshipping stores never reach that point, which is why the honest answer here is usually ‘not yet’.