I would want to see the "PowerMac" camelcase form be avoided. Apple do seem to avoid this in external docs, and when they use it internally its meaning seems to have settled on any PPC desktop Mac, including iMacs. For that generic case, "PowerPC Mac" or similar should get the point across to normal people.
It would be nice to leave revision letters and code names out of "real" article titles too. (redirects with models' pet names, e.g. Yikes, to make linking from forums more convenient would be another story -- and of course mentioning them inside the pages would be fine!).
The reason I'm proposing this particular scheme is that many users of this resource will be here because they have problems that need solving. It will make life easier for them if we're on the same page as Apple.
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Anyway, a scheme that would make sense to me is:
Power Mac == the generic term, anything that was originally sold as a "Power Macintosh" or "Power Mac"
iMac, PowerBook, etc. == those product lines.
PowerPC Mac == any Mac with a PowerPC inside.
Individual Power Mac product lines get the names they had when sold as new: Power Macintosh G3 (and older), Power Mac G4 (and newer).
Specific models get their
public names, in the style used by Apple
in AppleSpec and on their support pages. (True, we won't always know what those titles will be until after support docs start trickling out, but those will always be the latest models so the number of links to be touched up later will be smallish.)