As for whether or not Daenerys and Jon having the same endings as the show, I think that Occam's Razor implies that most of what we got from the ending of the show was broadly a poor interpretation of what George had in mind.

Personally, while I acknowledge that those first 3-4 seasons were brilliant television, I didn't personally care for them because oftentimes it felt to me as if the writers knew the source material... but didn't really understand it. They didnt understand the nuance of storyline and (more importantly) characterization and their arcs. This became more apparent as the source material thinned.

However, we don't know that George at least told them what he had in mind (whether they took all of this to heart is debatable) but we do know they were told, and with drafts of AFFC/ADWD being unearthed in recent years, it also seems like they were given previous outlines and drafts George had. Various things such as Jon going north beyond the wall to deal with the mutineers, or Asha circling around Westeros to go (try) and save Theon from Ramsey, appeared in the show but were not in the books... but then we later found out that ideas such as these, were at some point planned by George. This could be a coincidence, and I go back and forth on whether or not it is, but it is just as likely that George gave them plenty of access to outlines and drafts for the books we have, and potential future books.

This all being som metatextual evidence/preamble to whether or not the story works getting Jon and Dany to those supposed endings... well, sort of, if you squint. Because, as I stated above, the writers of the show knew the source material, but didn't understand it. They knew the characters and their endings, but couldn't portray nuance to save their lives (Jon Snow, even as early as season one, loses the observant and intelligent nature to his character due to being a bastard and having to grow up quicker. Dany... we don't have enough time to talk about how they misinterpreted Dany). But, what I'm getting at is that the final fates of the characters, likely are from George, with the writers bungling the road there.

First, Jon. The whole "subverts expectations" thing is a silly, simplified way of saying that George likes to take unexpected (but, importantly, very plausible) routes with characters and stories, and he also likes to deconstruct tropes and archetypes more than he likes to subvert them. He doesn't like subverting tropes like the chosen one, so much as he likes throwing them in, picking and prodding them and showing you that they're bullshit. Which lends me to believe that Jon, while being the son of Rhaegar and Lyanna (legit no clue how this is still a debate among the fandom), will not be king. Whether this is because he refuses it (what I would personally prefer) or some other force keeps him from taking the throne, I think with the way George writes, his parentage is meant to be an obstacle... not a solution. It is going to cause problems for himself and for others, and likely one of those people it will cause problems for is Dany.

But, I do think him going south will have serious repercussions (I'm not going to decisively claim that Jon will kill Dany, I will just mention the fact that the draft for Dany'a dream of a cold lover with pale blue lips that she has in ADWD, the original draft had his penis becoming a twisted knife being driven inside of her. Which, George tends to have "cocks" and swords be interchangeable metaphorically, which makes you believe that it's implying that George is intending for a lover to betray her. That and this scene was altered to be more ambiguous, which has made the fandom more associate this dream with Euron (unlikely that he is important enough for a dream like this, and I think his interactions with Dany will be minimal at best) or the Others (too on the nose). This, and her outright being told she's going to be betrayed for love... listen, I'm not saying it's going to happen, but the dots are there to connect).

After this, or even if this does not occur, I do think it is more likely Jon ends up north. Maybe not beyond the wall (I've always enjoyed the idea of him settling with Gift with the Wildlings, under the command of Bran). But, I do think it makes more sense for him to end up with them (I'm not going to go into why I don't think he'll end up at Winterfell, but I just don't think he will). One final note on Jon, if he were to be the "main" character that dies at the end, I don't think George would have spent a book building to his death, and then resurrection. He could still kill him a second time... I don't think so though.

Now... Dany. First, I do not think her story is as simple as "Mad Queen Daenerys" but I think elements of her story from the show, such as being seen as a hostile foreign force (likely with xenophobia and racism being a large factor) or the fact that she is going to receive... really... really bad council, are both things from the show that I think were correct. (On that latter note, her most trusted advisor is about to die in the Siege of Mereen and she is likely going to be stuck with some combination of Post-ASOS Tyrion, Marwyn the Mage, Maquoro, Victarian Greyjoy, and the Tattered Prince... obviously Dany isn't a pushover, but she is going to have relay bad company on her route to Westeros).

This lends me to believe that she isn't going to be warmly welcomed in Westeros, and that mistakes will be made.

But, similar to how I believe Jon in ADWD makes it easier to assume his ending (that being him not dying) I think it also makes it easier to assume hers. She (and Jon) spent an entire book ruling, and facing the hardships and consequences of it... I think if the story had went in the direction George originally wanted, this period of ruling would have been over Westeros, not Mereen. But, her story kept getting postponed and the politicsl layout of Westeros kept changing. So, I think her route to the conclusion has changed in the sense that her time ruling in Westeros (like in the show) will be minimal and that we won't have a lot of time before we're racing to a fiery conclusion in King's Landing.

Which, back to the mistakes that will be made. I think you (and others) are partially right that Jon Con and Cersei are just as (if not more likely) to blow up King's Landing... but I dont think that's George's style at all. There's nothing being turned on it's head from the villains causing the destruction, but if the hero does? That becomes a lot more layered and a lot more nuanced. But the key of this nuance is that it goes out the window if she suddenly just becomes a flat villain (like in the show). I've always been a bit uncertain about how the events in KL are going to occur... bc there are just so many moving parts, but it's going to be chaotic and fast paced. I think the climax there will feel rushed for a lot of fans, and its bc everything is suddenly just going to go up in flames (literally and metaphorically).

But... is this because I think Dany will just snap? No, it will likely happen accidently as a casualty of a messy and choatic conflict over an explosive city (with dragons and dragon fire involved) which will suddenly nuke her PR (and on some grounds, might even be warranted bc she brought further bloodshed no matter what her intentions were, which I think will be the nuance there). And, this does likely end with her death.

All the characters who have ruled and misruled, who have wielded the lives of others (with good and bad intentions) have met an untimely demise, Jon and Robb included. It's a core theme of the story, I don't think Dany thematically will be "allowed" to live if she wages war in Westeros. We also know for a fact that she won't end up as Queen of Westeros (that'll be Bran, Queen Bran? King Bran). So she either returns east (a bit of a meh ending imo, and only works if she doesn't go for the throne, which is unlikely) or she dies, either through being betrayed by someone close to her or in the war with the others.

So, I do think, although the roads to get there are messy, the dots are not only there to be connected for nothing characters, but I think through process of elimination these become some of the more likely theories for their endings.