They don't have the same approach : TMS Web Core generates the front as HTML/CSS/JS from the Pascal code.
UniGUI and IntraWeb générale a server program with create a dynamic web site : each page (or cal) is done to the server. You need to host it on Windows (IntraWeb/UniGUI) or Linux (UniGUI).
The three solutions allow to draw your client pages/forms in Delphi. (aka "the front end")
UniGUI / IntraWeb manage the server part. (aka "the back end")
If you want only server part, you have many Delphi project templates, components or libraries to work with, starting with WebBroker (included for all Delphi edition since many years).
Other samples : RAD Server (Enterprise/Architect editions), Delphi MVC Framework (open source from Daniele Teri), MARS (open source from Andrea Magni), ...