On top of what Dabs has said you would really like to go and use Electrum instead of merchant services like Bitpay and Coinbase commerce if you want to avoid some additional cost and of course unwanted KYC. What they'll just offer you is the convenience of having the html code ready to be plugged into your website and also the availability of liquidating your BTC payments quickly in your bank but you'll be paying Bitpay and Coinbase a cut of your earnings on every transaction you make with them. Here is Electrum's official guide on applying your Electrum wallet as a payment gateway for your website.