I'll just answer your driver question: you bring whatever you want. Our VMs just boot off of bytes you have stored in your image (which is in turn just stored on GCS). If those bytes happen to be Debian 8 with some AMD driver that supports the 9300, awesome ;).

We will be working with both vendors to make sure we highlight which drivers work most reliably on our stack though (virtualization + GPUs is way too rare!). We want to work closely with both vendors to do the qualification, so you at least know what is known good.

Disclosure: I work on Google Cloud.