@raudi1 

In Horizon, you either choose RDSH or single-user VDI. 

RDSH is always based on a server operating system with MS Remote Desktop Services role installed (Terminal server)

Single user VDI is mostly based on Windows 10/11 but you can also use server-based OS (2016/2019/2022) without Remote desktop services role installed. Then it will be used as a single user VDI instead of RDSH.

Not sure what you mean by "a full operating system might be deployed for each user". You always need a full operating system. 

There's a difference however between "published applications" and "full desktop" for the user. In RDSH environments, you can choose to only publish applications so the user doesn't get the full RDSH desktop, but only the application the user needs, or published desktop which gives the user a full desktop on the RDSH farm (including start menu, taskbar, ...). In the single-user VDI situation, the user mostly gets a full desktop VDI, although it is now also possible to publish applications from a single-user VDI in Horizon (in that case, each user will still have its own dedicated VDI, but only see the published applications, not the full desktop)

Hope that makes it a bit more clear.