Web Station will takeover the NAS's TCP ports 80 and 443 (I've always had WS running so never not had this assignment but I hear that when WS is not installed then these ports can be used for DSM portal itself).
In Package Center you can install Apache HTTP Server (2.2 and 2.4) and PHP (5.6 and 7.0-7.3). So, along with Nginx, you can select which web server technology and PHP will be the default for the virtual hosts run by WS.
There's a default virtual host that uses the /web Shared Folder as the document root: stick an index.html file in here to get your web site running.
You can add your own virtual hosts that have their own document root which may be another Shared Folder, a folder in another Shared Folder, or a folder within /web. The folder must permit the 'http' user group to access it (look at the user permissions of /web). These can have different web server and PHP from the default.