Why did you look for other sources of APIs the Bitcoin core or full node itself has RPC API you don't need to look for other sources unless you don't want to run a full node.
FYI, even if OP or someone else doesn't want to run their own full node, they could use service (such as getnodes.io) which offer Bitcoin Core API.
At a glance, the list looks decent although it doesn't contain any service which designed to accept Bitcoin payment (such as Coinbace Commerce).