we want to develop our current shopify to be a APP too, for the purpose likely a "quick path to buy" with the smartphone.
Is there any recommendation from the members where we need：
1. use only the app can sync the info from shopify & officially support from shopify too, in order to prevent any incompatible if any upgrade from shopify. If possible, source from the shopify official APP directory in the shopify backend.
2. must use the shopify payment gateway instead of one more payment gateway from that standalone app
3. check with that app must support with any specific shopify award & loyalty app together and sync with any data