In addition to the answer above:
IMHO, you should use tags #personA #personB IF you don’t plan to add information about only this person somewhere else.
I mean, for example: if you created notes about some trip/situation or something else where some Person was involved AND you don’t want to make separate page about this Person to note interesting facts, hobbies, etc, i.e. information specifically about this Person, than I would use tags.
In other situation, I would use links with backlinks or another way of organizing links like MOC.
TLDR: If you found that you need to add more information specifically about the tag then use links and pages.
Next:
I am struggling with the way unlinked mentions work - would/should I see an unlinked mention on my daily note pointing to my standalone page on a particular person or only from the standalone page back to my daily note? At the moment it’s the latter.
If I get this correctly, no, you wouldn’t. @macedotavares is right, you can see unlinked mentions ONLY to page that you’re viewing.
So if you have 2 daily notes and one of them have [[Person1]] link, and other have only Person1 in text without link, then on page Person1 in backlinks you will see one linked mention from first daily note and one unlinked mention from second.
Also, if you create linked mention to non-existent note, link will have different color, so you will see which note has not been created yet.