You're stuck with cloudflare nameservers¹, so if you want to change nameservers you need to transfer them to other registrar, how much of a deal breaker this is is up to you, to me is project dependent.
> 6.1 Nameservers. Registrant agrees to use Cloudflare’s nameservers. REGISTRANT ACKNOWLEDGES AND AGREES THAT IT MAY NOT CHANGE THE NAMESERVERS ON THE REGISTRAR SERVICES, AND THAT IT MUST TRANSFER TO A THIRD PARTY REGISTRAR IF IT WISHES TO CHANGE NAMESERVERS.
there are very few parts of that contract in all caps, but that's one of them :/
That's annoying. For some use cases, not a big deal. But I have used the AWS Route 53 'alias' functionality on a number of occasions and that requires the use of Route 53 nameservers.
1. Section 6.1 of https://www.cloudflare.com/domain-registration-agreement/