Note that the Romance of the Three Kingdom is different from simply Three Kingdoms. Luo's portrayal of the time period and accuracy of important events are right on the spot - it's other aspects of the novel that deserves the attention.

Easily the first thing you would spot is the author's bias in favour of Shu Han. I have mainly criticized the novel based on his favouritism, and not of historical accuracy, but there are things that are contested. For example, Guanyu's weapon the guandao wasn't invented during his time. In more accurate texts, Guanyu is described to have kill his opponents by 'piercing', which is a word attributed to halberds or spears. Halberds are more common among generals during the Late Han-Three Kingdoms. He also made up a significant amount of fictional characters that doesn't have any historical backgrounds. The obvious one is Diao Chan. Some of the personalities attributed to certain figures were completely skewered for Luo's own purposes. Such one would be Zhang Fei. In fact, the historical Zhang Fei came from a prestigious background. He was well educated and a brilliant thinker and is also an artist. He authored a piece of art depicting a peach garden which inspired Luo to come up with 'the oath of the brotherhood in the Peach Garden' although in reality the brotherhood was only shared between Guanyu and Zhang Fei. Luo was however correct about Zhang Fei's ill-temper. Many other more problems but I don't think this is what you're mainly asking for.

I fail to recognize any inaccuracy in terms of time and significant events.

Speaking of Water Margins, the first 36 characters were indeed inspired by people who may have existed, bu the following 72 are completely made up and never existed. Water Margin has no background context to support its story other than general facts, such as Song fighting against other rebellious states and that the government was highly corrupted. The novel was in fact authored by two persons - Shi Nai An and his student, well again, Luo Guanzhong. Shi wrote up to the amnesty of the bandits, and from then Luo wrote the rest.

I understand that these are huge influences of the Chinese culture, but its portrayal are far from accurate. Let's not get into the Wuxia genre or Monkey King.

I'm sure you're aware of the adage regarding ROTK, in that it's 2/3 history, 1/3 fiction. As a segue, I notice that the Chinese seem to love that formulation because that's how they characterize Mao, as 2/3 good, 1/3 bad.

That said, there are definitely a ton of small anachronisms in Luo's version with what's known of the history at the time. I remember raising an eyebrow when I saw a mention of a character who was a "failed examination" candidate. The examination system, which was so prevalent in Ming times, got its start in the Tang Dynasty (though restricted to the aristocratic families) and really took off as we know it in the Song Dynasty.

But with that said, I don't know think that Romance (or even Records) of the Three Kingdoms is "that" accurate if you want to take a deeper historiographical look, rather than taking even Chen Shou (author of Records) at face value. The events as recorded in the chronicle likely happened, but its the meaning (always the meaning) of those events as interpreted by Chen Shou and later historians that is subject to scrutiny.

If you want the best history we have so far on the subject, check out this article written by noted post-Han scholar Rafe de Crispigny, which is luckily available for free on the internet.

https://digitalcollections.anu.edu.au/html/1885/42048/3KWJin.html

This was originally written for what was supposed to be the Cambridge History of China vol 2., covering the post-han pre-sui years, but for some odd reason, that book has still not been released.

It's a bit more thorough, and leaves as many blanks as it fills, but it'll give you a better grasp of what historians, as opposed to romanticists (of which you have to be careful of with regards to mainland Chinese scholarship) actually think of this era.

His section dissecting "what really happened" at Red Cliffs is fascinating, and worth the price of the read alone. If you want the tl;dr version, basically Cao Cao was defeated at Red Cliffs in what might have been a far smaller skirmish. Over time, the contemporary chroniclers played it up in order to suit their politics.

I don't mean to hijack this thread, but I've always been curious about Shu and the the myths that may have been portrayed as truth.

First is Liu Bei. He is made out to be one of the most virtuous and kind people one will ever meet. But then how would one explain him betraying his family member and invading their territories. So in short, how much truth is their to the persona of Liu Bei.

Second is the Sleeping Dragon: Zhuge Liang. Obviously he didn't actually summon a different wind in the battle of Chi Bi, but what about his tactical and strategic ability in general. Was he truly a mastermind without peer and one of the greatest strategist of all time, or can this be attributed to Luo's "love" for Shu.

Also any clarifications on Zhao Yun would be spectacular, but I realize I'm asking a lot so if you want to bypass him then please don't feel any need or desire to mention him.