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My biggest thing about tags is that they are for searching, not describing. If you are likely to search for 'amateur' or 'blonde hair' or 'favourites', that may be much more useful to you than person names. If you do not know the name, I recommend you leave that blank until you do. If you sync with the PTR and these are likely to be on some 'realbooru' or similar, another Anon will probably eventually add the right person: tags for you either manually or by parsing a booru they are on.
If these are for 'my tags', you can of course do anything you like, but in general, I have learned that trying to tag everything you see, or try to do anything like a 'perfect' job, is a rabbit hole with no end and very low productivity.
You could try a kind of 'artist request' tag for 'person' if you like, like 'unidentified person', as a 'my tags' tracker just so you can revisit these files at some point.