How accurate is 'estimatesmartfee' in bitcoin-core? Method of estimatesmartfee is very simple and easy to use and understand. But I want to know how accurate this function really is? It would be great help if you can provide a link to article or Research paper.
I have found this article https://bitcointechtalk.com/an-introduction-to-bitcoin-core-fee-estimation-27920880ad0 which give you a pretty good summary of this bitcoin function.
Notice that estimatesmartfee return is based on the data of what happened in the past in the blockchain, it is not trying to predict what will happen in the future but what should happen based on what happened before, maybe you will find a better algorithm if you think that there will be something new that will disturb the market.
From the article:

A more sophisticated algorithm may attempt to be more forward-looking.
However, the more complex the algorithm, the more difficult it becomes
to describe its operation and results, and the more difficult it is to
argue that the algorithm is safe against manipulation.