Both DNS over TLS and DNS over HTTPS encrypt plain DNS queries from the phone.
DNS over HTTPS uses port 443 and DNS over TLS uses port 853. In some networks, one of these ports might be blocked. If port 443 is blocked, you should use DNS over TLS. If port 853 is blocked, you should use DNS over HTTPS.
In some cases, DNS over TLS may be faster than DNS over HTTPS or the other way around.