Every thing transfered between the two machines is encrypted on the server, send to your machine then decrypted, and shown to you.
Even the contence of the x-app, what it should look like, etc..
So in this matter the CPU-power of the two will have an effect aswell.
If it's browsing, then the transfere will be like:
- you click a link in the browser started from the server.
- your machine encrypts the fact that the app should have a mouse click at possition(x,y)
- server decrypts the possition, sends it to the x-app.
- the x-app enterprets it to follow the link and tells the server to fetch the new page.
- The server fetches the page, and tells the x-app to show it.
- The x-app wants to show it, so it tells the server to encrypt the contence, and send it to you.
- The server sends the page-contence encrypted to your machine.
- Your machine decrypts the contence and displays it for you.
Kinda a long way for just the contence of some HTML code..