That conversation when you say you just keep on trying and he says thank you for giving him hope, makes me really worried I may have inadvertently encouraged him to do something really stupid. I have found it much more revealing to have him as a friend than a romance because I can keep a more impartial view on what he says and not get distracted by those heart icons. Trying to fathom him out though is well nigh impossible. Just when you think you are beginning to understand where he is coming from, he springs something different on you.
I don't think he regards modern elves in any way as "his People". I had a hilarious conversation after we got back from the Winter Palace having made Briala ruler through her puppet Gaspard. I commented that I hoped it would help our People. For a moment he was genuinely puzzled and then the penny dropped "Oh you mean the elves". I was thinking, "Of course, what did you think I meant?" I was laughing to myself because he was clearly thinking about someone else and yet of course the elven Inquisitor isn't able to pursue the matter with him.
Then later when Abelas pointedly says "You are not of my People" to Lavellan and yet acknowledges Solas as an "elvhen". Once again, apparently Lavellan completely misses this and never thinks to question him about it. Plus the way he puts down Morrigan when she is repeating the history of Fen'Harel that is told by the Dalish. Even stranger is that after you have actually met Mythal, any Inquisitor, much less an elven one, doesn't race round to Solas and say "Guess who I've just met?" or alternatively, if Solas was actually there, "What did you think of that?"
There is also the matter of spirits. I had always assumed the reason he was so upset about what the Grey Wardens were doing was that they were harming spirits by pulling them through the veil and binding them. Not a bit of it. Rather as with the Briala/elf speech, I said something to the effect of don't worry we'll help the demons and once again he didn't immediately get why I would be saying this, before recovering himself. I assume from this, therefore, that what was bothering him was that they were intending attacking the last two remaining old gods and he disapproves if you recall all the achievements of the Wardens in the past because that included slaughtering the previous five.
So I think any People he intends to help comprise the ancient elves, like Abelas, who are still to be found in the far reaches of Thedas, and the elven gods, wherever they may be. Even if we don't have to kill him, I wouldn't be surprised if he unleashes another bad guy (or more than one) on Thedas and we have to clear up his mess for him. I'm hoping that Flemeth/Mythal's plan involves avenging herself on them, so she had to let him have her power in order that he could release them (because he is the only one who can) but that she has a contingency plan (probably involving Morrigan) that means that she will be aiding the PC in order to finally gain her revenge.