Hi
I'm not sure, on the software I've used it seems to know where the restore goes but gives you the opportunity to choose a location if you want to.
As for using drive letters that's really hard to say because when I boot into my restore disk the drive letters have all changed from what they were when booting into Windows.
To avoid confusion I name my drives i.e., C:\Windows 8, C:\Windows 10, D:\Games etc.
I also take note of the exact size of the drives, this can help identify them if the drive letters come up different.
Note that both of my C:\ drives are on different hard drives but both will appear as C:\ when you boot into that version of Windows.
Both of my backup programs, EaseUS TODO, and Paragon seem to default to the...