Your isp can most likely tell which VPN you’re using (unless you also use tor, and even then there’s the theories that a lot of it is ran by law enforcement… depends on how paranoid you are), they will still see the quantity of traffic coming from your home to the VPN and vice versa. All they need to do is to check the IP and they’ll likely find it’s in use by … VPN service.
As long as using a VPN is not illegal in your country you can pay for it however you want really (in some places paying with crypto may make it more suspicious than if you just paid for it through PayPal), if law enforcement really wanted to find out the VPN service you use they probably could, the payment would only make it a tiny bit easier.
The key point as mentioned multiple times is to use one you trust, there’s no objectively best one, but you’ll find a lot of objectively bad ones (for privacy) if you research them. As a start just never use any which are sponsoring YouTube videos or blog articles, pretty much all of those are crap.