The options shown at the initial installation are really just a list or group of packages to be installed. So a Server installation will include such things as httpd and a Workstation installation will include stuff like Libreoffice and Gimp.
After the initial installation you can customize your installation to whatever you think you need. The groups are just a starting point. Add or delete packages as you need them or don’t need them. After the initial installation there’s no distinction between a Workstation installation and a Server installation. It’s just a difference in the list of rpms that were installed when you set it up and you can change that however you wish. You can have Libreoffice on your Server installation and httpd on your Workstation installation if you want.
When I do a setup it really doesn’t matter what initial option I choose. After the initial setup I have a list of rpms that I want to install and a list of rpms that I want to remove. The starting point (server or workstation) doesn’t really matter.