Do windows in Firefox e10s have different process IDs?

Will new windows in Firefox e10s have a common PID or different? New tabs definitely have different PIDs, I know that.

Will windows of different profiles have different PIDs?

Stuff like this is an implementation detail, and since the implementation isn't finished yet, there is no definitive answer (and even if there was, it might change in future releases without warning).

But right now, IIRC, the following is true:

• All UI is "owned" by a single process (the main process).
• New top-level windows fully belong to the main process.
• Tabs might be "remote" aka. "out-of-process" (e.g. content tabs will be remote, while some other tabs will be still living in the main process, such as certain about: URIs).
• Regarding profiles: Nothing changes on that front.

You can already try this out in Nightly builds (There is a "New e10s window" menu item).