Are you sure PayPal supports BTC and other crypto? Because I can't find a crypto option or wallet on my PayPal account, it only supports local currency.
Or is PayPal BTC not supported in my country yet?
Anyway, I think it's not a good idea to use PayPal to buy something online and settle it with BTC using PayPal.
You don't have full control of your wallet; it's still good if you have a non-custodial wallet.
It's limited to the US and you're paying using BTC from your paypal account that has BTC in it, not sending BTC to certain address so in a way you're just using paypal account with balance

and yes it's 100% custodial wallet with paypal.
There are many alternatives out there but merchant usually just don't care and what matters most is getting the USD converted amount.