It does not seem that there is enough here to determine one of those three categories would best fit, as the context is focusing more on the one which is lost than those which are not lost.
To get a little further context, here's the text translated "ninety and nine just persons, which need no repentance":
ἐννενήκονταεννέα δικαίοις οἵτινες οὐ χρείαν ἔχουσιν μετανοίας
I have highlighted some things to note. The second part is what the question focused on, and yes, it clearly is saying that they "no have need" to repent. So, it is clear that literally, they don't have a need to repent. However, I also wanted to point out the first word highlighted. In the Greek, an adjective, "righteous", unlike English, does not need a noun to modify. We had to put that in. So, while it is good in English to translate it as "righteous person", it could just as easily be "righteous thing" or "righteous creature", etc. Therefore, from this text alone, he could just as easily be referring to angels, people who already repented, or even the types of theoretical people you mentioned. Whatever these things are, for the sake of this passage, they actually do not have any need to repent. There are many things which have no need to repent and are righteous.
Who are what these things are is the weakest part of this text, meaning that rather than forming a doctrine from what these things are, one would be better to question what these things could be by the rest of their understanding. For instance, if you believe that there are people who already repented so that they need to have no further repentance at the moment, then you might assume that is who he was talking about. Other passages focus more on the universal need for repentance, and so we can rule out people who never needed to repent, though not from the text itself.
These verses are there to show to the Pharisees, who thought they were righteous, that their state, even if it were so, is not better than those who are indeed lost but then found. The final account in this passage is the Prodigal Son, which is a rebuke of the Pharisees who only thought they were already righteous sons, but who Christ shows that they should be rejoicing in the return of the sinning brothers. It seems to me that Christ, in his diplomatic way, was not attempting to focus on whether there actually were some righteous people, avoiding condemning or confirming the Pharisees, but on the fact that being found would be even more of a cause for rejoicing.