For the dropdown form filling question: This is not a standard HTML dropdown but a custom design. That is why the regular Selenium IDE-style select command fails. But XClick and XType can automate it. See here:
In the screencast we select Bulgarian as language. To do so, we first click on the dropdown to give it the focus and then use XTYPE to send the KEY_DOWN and KEY_ENTER commands.
For the 2nd question: Google remoted desktop automation should work as well with XClick and XType, see Codeless UI Testing. Automated GUI Testing and Monitoring
We use UI.Vision RPA software to automate RDP all the time 
Please let me know if you have any further questions.