Nick here from Shopify.
Can I ask which country you are based in and what currency you are looking to accept payments in?
You can have one payment gateway for credit cards and all types of payment and then a gateway for PayPal also. You can see more about adding a third party payment provider here.
If you wanted to create your own Hosted Payment SDK, you can do so also, but it can be complex and you might need to hire a Shopify Expert for help with that. You can see more about Hosted Payment SDK here.