Correct way to modify config files in an upstream RPM?

What's the right way to create an RPM that modifies the %config(noreplace) files installed by another RPM? Specific instance of the general question: We want to modify the repository definitions installed by almalinux-repos so that the definitions have a baseurl pointing to our internal mirror. Because the repository definitions are %config(noreplace) in almalinux-repos, we could modify them any number of ways. However, we'd like to have our modifications packaged as well. One idea is to create a new package that Obsoletes: almalinux-repos. This would suggest using almalinux-repos as a BuildRequires and then including its files in the buildroot. It's so easy for Obsoletes to go bad that we are averse to this approach. Another idea is to create a new package that Requires: almalinux-repos and then uses %patch to modify its files. Secondary question: Assuming we use the %patch mechanism, should we add Supplements: almalinux-repos to our new package so that it is automatically included in package resolution?