As a general rule, I only install from official RH supplied repos, but sometimes I have to build my own RPM file, for example I'm not aware of any anti-virus software in the official repos.
In RHEL7, I was able to separate my custom installations into /usr/local, keeping them well away from the official RH software.
In RHEL8, there seems to be a problem, due to a change in Fedora, nearly all RPM installs will want to create files in location /usr/lib/.build-id (to improve debugging).
BUT, this means I can no longer keep my RPM completely separate from the official RH supplied software. I don't think you can specify '/usr/local/lib/.build-id' instead?