installation directory question

Wise-folk,
RHEL installation on a VM, installed WP in /usr/var/www and configured correctly. Added three databases for three sites. Using Apache and Mysql.
After some RTFM, I would like to install several sites. But apache root is holding the first site.
1 – Should I move the first site to /usr/var/www/site1 and add additional sites as such?
2 – How to move the site?
3 – Or use a network and run all from one WP location? Is this best practice? Are there drawbacks to this configuration? Advantages?

Thx,
Harry