I used to have a really cheap domain from Namecheap before, and I used Cloudflare as my DNS. I'm going to buy a new domain, and Spaceship seems to be the cheapest registrar for my domain right now (I'm only buying for one year), however they seem really new. Are there any differences between Namecheap and Spaceship, and should I use one over the other?
The first year price is a "loss leader" discount. Get you in the door, then make a profit from you in future.
Namecheap have a bit of a reputation (as can be seen here with a few people warning of poor support), Spaceship seems to be a bit of a offshoot/addition they have created, partly as it doesn't seem to be a 1-1 comparison, and partly maybe to avoid their existing reputation?
However, it's not entirely a bad idea to separate your registrar from your DNS provider. If one goes down, you still have access to the other to make changes. I used namecheap in the past because it was cheap, and cloudflare for DNS. If you are using both for only your registrar, it probably won't matter much at all as you are probably not changing nameservers often, if at all, once set.