yes you can. but for mobile devices you cannot rely just on your home router. because those would not work when you are on cellular networks.
android pie has internal support for private dns so you don't need to install additional apps.
excitel does not let you use third party dns unless you use encrypted dns. all unencrypted queries are processed by excitel even if your devices are set to use third party dns.
excitel's own dns is logically likely to give you better performance on services peered with them but i haven't really noticed any difference in performance.