You can configure caddy to use 80 and be a reverse proxy for both the services, serving one site or the other depending on the name (you will need a second DNS entry pointing to the same IP).
about not exposing 443, I really doubt that caddy can automatically retrieve SSL certificates for you if not running on the default port. Check the documentation, if I’m right either you open an empty website on 443 just for the sake of getting SSL certs to run https, and manually configure the other port to do the same, or you get the certificates manually using the DNS verification (check let’s encrypt documentation) and configure caddy to use them.
You can configure caddy to use 80 and be a reverse proxy for both the services, serving one site or the other depending on the name (you will need a second DNS entry pointing to the same IP). about not exposing 443, I really doubt that caddy can automatically retrieve SSL certificates for you if not running on the default port. Check the documentation, if I’m right either you open an empty website on 443 just for the sake of getting SSL certs to run https, and manually configure the other port to do the same, or you get the certificates manually using the DNS verification (check let’s encrypt documentation) and configure caddy to use them.