By my power as necroposter I raise this thread!
W3 endings and book chronology could actually be conceivably tied together. If Radiovid is alive.
We know several facts from book lore:
1272-1276 - witch hunts took place, which at some point claimed life of Philippa Eilheart, tortured to death for alleged or real attempt on life of Highearch of Eternal Fire. Canonised as a martyr by magocracy in following centuries.
1290 - Emperor Emhyr var Emrys dies, who ruled with his wife Cirilla. Whom we know to be not the real one, but thats not the official truth of the Empire. Succeeded by Emperor Movraan Vooris.
And the fact that if took many more decades and Emperors for the Empire to batter North to full submission, Kovir and Poviss being last.
No organised wide witchhunts would be possible nighter under the rule of Emhyr nor Dijkstra. Under Emhyr only, exclusively only those who he orders to are burnt at the stake and no religious institutions are allowed to interfere with interests of state. Rows of gallows and chopping blocks, or killing wealthy to nationalise their property does not disagree with Dijkstra, but he won`t tolerate fanatics of Eternal Fire in his Redania, anyway you look at it. It does, however, work for Radovid, at least for now.
So, to answer the question who should be ruling North at 1272 in accordance with book lore, game provides us only with one answer - definitely Radovid.
It is achieved by actually not meddling into politics and not letting be dragged into regicide plot with cheap bait of "doing this for Triss, for Yennefer" by Dijkstra. Which is exactly how book Geralt would act.
From Radovid having firm grip on Redania game goes on to telling as about assassination of Emhyr by the opposition who saw his failure to acquire more gains in war with Northern Kingdoms as sign of weakness. Here we can make a jump of logic and say that this plot could develop to its fruition only by 1290. Thus Emperor Movraan Vooris ascends on the throne - which is actually not the first attempt to put him there, previous failed before Battle of Brenna. Should be noted that plan to made real Ciri Empress in haste to discharge political tension in the Empire would very much against established fact that Emhyr remained in power for 18 more years.
Lastly, fates of the heros. With all said above, none of choices left are actually upsetting book lore, since both Geralt and private person Ciri are quite below grand historical radar. Whither they both live or die, does not make impact on history books at that point.
If they live, however, then Ciri lives to the nordling tale "Witcher and Witcheress" and Geralt retires with his one true love... sorceress Yennefer of Vengerberg.

Triss Merigold making sadfaces, sidelined, again. Arguing who is she, the one woman for him, is really pointless, book lore wise.
So.
Witcheress/Radovid victory/Retirement with Yennefer fits rather agreeably.