Yes, there’s a conflict – same as others have reported:
In file included from /usr/include/QtCore/qdatastream.h:46:0,
from /usr/include/QtCore/qmetatype.h:49,
from /home/angelman/opt/Qt5.9.1/5.9.1/gcc_64/include/QtCore/qobject.h:54,
from /home/angelman/opt/Qt5.9.1/5.9.1/gcc_64/include/QtCore/QObject:1,
You can see that it’s originally including your headers from your downloaded version in /home/angelman/opt/Qt5.9.1/, but then ends up bringing in headers from your main distribution package in /usr/include.
Looking at the package listing for Qt5 on CentOS 7, it looks like the system-supplied version is 5.9.7, which is more recent than the one you’re trying to use. I’m not sure why you’ve downloaded version 5.9.1 – the most recent version in the Qt5 series is 5.15.2. My suggestion is to remove your downloaded version and use the distribution-supplied version as it is…