Hi Krish,
There is no direct answer to this question. Even if there is something called best combination, bad level of coding can degrade performance.
1. EXT JS (classic ui) and CORAL UI (touch ui) is more of a framework in which Authoring part is built for AEM
2. When it comes to AEM 6+ - Sightly and Java is normally used for development
3. Apart from Sightly + Java, If your application requires client side interaction Angular JS is good framework to use
hope it helps
Thanks