EdelingF
do I also have to reinstall contribs I no longer need?
Theoretically no.
As this may leave config information & templates still installed on your system (from the restored backup), it may be wiser to reinstall the unwanted contrib and then uninstall it, which should remove unwanted config info & templates.
how do I find out which contribs I have been installing?
You could compare the rpms installed on your old system and your new system.
You could review the server manager panels and see what contribs have been installed.
You could do
rpm -qa rpmname
to see what contrib versions were installed on the old server.
Use your memory.
For the future, it is wise to create an ibay where you religously copy every contrib/rpm that you install.
This ibay (and contribs) get included in regular backups. When the backup is restored on your new system you also have all the contribs you need to reinstall readily available, just
cd /home/e-smith/files/ibayname/files/...
and start reinstalling.