BigBuy has 3 different dropshipping services and sometimes could be difficult to understand which one is the right one for you but if we exclude the Base one which does not offer any API connection (so you can't submit orders for instance) the other two are pretty similar.
The only difference is that the Pack Marketplaces includes their dropshipping app which is unuseful if you are already using ApiDrop.
The bottom line is that the Pack Ecommerce is the right one and it is perfectly integrated with ApiDrop.