AVD

In Addition to Chris's advice below, Microsoft has a page detailing their sizing recommendations for the session hosts: https://learn.microsoft.com/en-us/windows-server/remote/remote-desktop-services/virtual-machine-recs

Multiple Application Groups are useful when you need to separate out access to different apps for different people. But if all 20 need access to the same apps, then you could put all the apps in the same application group.

And there are 2 types of Application groups, desktop and remoteApp. The desktop one is default, because you want the users to be able to log in to the desktop. Since you want applications to be listed in the desktop rather than separate applications outside desktop, you do not need any remoteApp-type application groups, just the desktop one.

To add apps to it, in the azure portal I believe you go to Azure Virtual Desktop > Application Groups > (select your application group) > Applications > Add
Here you can add your MSIX packages.