The installation on a NAS should be very simple. In the case of QNAP there is a standard facility to create virtual hosts, which means you can have many sites, each with their own unique domain pointing to the IP address of your site, and the NAS will (based on the domain name requested by client) redirect to the correct website (just like magic!).
Each of these Virtual sites could be WordPress, Drupal, Joomla or any of the other add on applications provided with QNAP QTS.
Under the covers its the Apache server reverse proxy that is doing the work, but the QNAP management console shields from all this.
The only variation being that if your running a Virtual host using Virtualization, you will need to make alterations the the /etc/config/apache.conf/extras/.. files to make it redirect to another IP address. This more advanced configuration is provided as a part of the smikbox service, and outside the scope of this topic.