The biggest breaks from established canon seem to be: 1) making Miriel a Ruling Queen for a significant amount of time with Pharazon as her chief advisor.

that "leak channel" seems to be part of a conscious effort by Amazon to repeat the "fan leaks" of twenty years past.

I don't think Miriel will be the ruling queen just yet. She'll probably be queen in the sense of ruling for the still-alive but infirm Tar Palantir (Geoff Morrell?): dramatically, it doesn't make sense to rid of Tar Palantir until the time of the coup, which sounds like an end-of-season event.

Tolkien's description of Ar-Pharazôn in "The Peoples of Middle-earth ":

"He was a man of great beauty and stature, in the likeness of the first kings of men; and indeed in his youth he was not unlike the Edain of old in mind also, though he had courage and strength of will rather than of wisdom, as after appeared, when he was corrupted by the counsels of his father, and the acclaim of the people. In his earlier days he had a close friendship with Amandil son of Numendil, Lord of Andunie, and he loved the people of that House, with whom he himself had kinship (through Inzilbeth his father's mother)."

In Tolkien's description, Ar-Pharazôn strikes me as a charismatic man of action, and not at all as a "very intelligent and [..] consumate politican". The professor of course offers us little to fully flesh out the final king of Numenor, but it would be far more authentic to (initially) depict Ar-Pharazôn as a physically imposing, highly inspiring warrior, in fact full of youth and vigor, someone not just liked by the Numenoreans but by the viewers themselves (this is critical!), who is eclipsed by his hubris, and then, when the first signs of age start to show, slowly deteriorates into what he becomes in the end. I fear the show will immediatly turn Ar-Pharazôn into the Other, the scheming (as in having to scheme because he lacks martial prowess) politican who operates in the shadows and only cares for power. Again, it is too early to say for sure, but the "leak" certainly does not sound too promising.

As for the picture you posted: Gravelle looks like a stereotypical pirate or a Dunlending from Jackson's second film in that shot, certainly not like a Numenorean.

The most likely scenario is that Amazon is intentionally feeding "leaks" to the "Fellowship of Fans" channel as part of their (currently very diminutive) marketing strategy. Such "leaks" have become a common method in movie/TV/video-games marketing over the last ten years. This does not in any way mean the channel is on Amazon's payroll, but simply that after one or two genuine leaks in the beginning, Amazon's PR team decided to feed the channel piecemeal leaks about the series. If Amazon did not want to see those leaks, they would have forced the removal of the channel long ago (another possibility, of course, is that "Fellowship of Fans" is inventing all leaks out of whole cloth, but I doubt that).

You might be correct, though I'm not convinced that Tar-Palantir still lives at this point of the show's timeline. I suppose that we could see Míriel acting as her father's regent, but even that seems to goes beyond the history of Númenor as we know it (as far as I'm aware).

I think it goes like this:

Tar Palantir is old and leaves the affairs of the realm to Miriel.
Pharazon gains political powe as her right-hand.
Palantir dies.
Pharazon performs a coup d'etat.
Miriel is forcibly wedded to Pharazon.

Imperious, arrogant, not particularly likeable

At some point in season 1 he will give an amazing speech to the Numenor crowd

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"this point" is believed to circa episode 3 of season one, so its really not that far into the show. We KNOW Tar Palantir is a character in the show, and if I were Amazon I'd milk the "old infirm king" thing for all its worth - rather than having him corpse in the second episode - but to foreshadow's Pharazon's own fears of old age, but also just because it creates an interesting court dynamic.

I think it goes like this:

Tar Palantir is old and leaves the affairs of the realm to Miriel.
Pharazon gains political powe as her right-hand.
Palantir dies.
Pharazon performs a coup d'etat.
Miriel is forcibly wedded to Pharazon.

That would line-up with the idea of him still being alive, but having Miriel rule for him.

Its basically Gladiator where Commodus gets the girl...

"This name [Tar-Palantir] Inziladun took, because he was far-sighted both in eye and in mind, and even those who hated him feared his words as those of a true-seer. He also would spend much of his days in Andunie, since Lindorie his mother's mother was of the kin of the Lords, being sister indeed of Earendur, the fifteenth Lord and grandfather of Numendil, who was Lord of Andunie in the days of Tar-Palantir his cousin; and Tar-Palantir would ascend often to the ancient tower of King Minastir, and gaze westward in yearning, hoping to see, maybe, some sail coming from Eressea."

certainly not a break with the lore and moreover since Tar-Palantir was so often removed from the capital spending time with the Lords of Adunie or gazing out of a watchtower or indeed prophesying as a 'true-seer', it would be natural that just as Ancalime ruled as regent on behalf of her absentee father Tar-Aldarion a similar set of responsibilities would fall to Tar-Palantir's heir and daughter Míriel.