VPNs usually route your DNS through them as well, sometimes to other DNS servers but sometimes they just send them to your original DNS server but through the VPN, kinda up to your VPN config - all of the vpn services I’ve used to date did this, although they were all reputable ones. I’d not recommend to use a questionable VPN though.
Dnssec only verifies authenticity of the server and the integrity of the data, so it helps to prevent man-in-the-middle of DNS, it doesn’t provide privacy. Look into DNS over Https (DoH) instead. It provides e2e encryption for your DNS traffic which achieves what dnssec does, but also gives you privacy. DNS over TLS (DoT) also does this, but it runs on a different port so it’s easier to block (e.g. if your isp decided they don’t like private DNS), while with DoH your DNS traffic looks the same as other web traffic - and afaik it can’t be blocked. As above, it’s likely this is not needed for use with a VPN, but I’d recommend looking into in general for use even when not on the VPN. Things like controld or nextdns can give you even more peace of mind (although read up on their policies for yourself)
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.