Virtual App and on demand streaming

I am new to SVS/ Thinstall/Softgrid and still trying to understand the app virtualization concepts.

Q for the gurus - Once I have created the virtual file (.EXE, .VSA, or .Sprj) file
1. Can I have the virtual app available via a website link? Essentially, can these virtual apps be on-demand to the user? This would be mostly for disconnected users - mobile users. Users from anywhere in the world shoul;d be able to go to a secure website and click on the virtual app file and voila the user can use the app without issues.

2. If yes, would the user need the a client (SVS client or Softgrid client) running on the machine? Can the on-demand streaming be independent of the softgrid client on the user's machine? (Does Thinistall achieve that?)

3. Would this also involve the SVS Streaming Server / or Microsoft Application Virtualization server component in the backend?

Also - how do customizations get retained in Virtual apps? Eg. If I am a new user. I installed Outlook by clicking on the virtual app. I customized my signatures etc. Now, where do these customized settings stay? Is everything the same as a standard app? How does the situation change if I have roaming profiles? How does a Virtual App handle roaming profile?

Thanks

Thank you,