Share Point Online Integration with .net windows application

I am a .net developer and developing windows application where i want to integrate with sharepoint online 2016 and not have the much knowledge that which is the best approach to integrate .i have googled and found three main solutions

1) Using CSOM library where i am facing a bit performance issue.

2)Using REST API -don'thaemuch exposure on this

3) CSOM using server side library

 

But i am really not sure that whih one should adopt andhow to implement in best approach where i can handle the performance issues as well.

 

so could you please explain that which is the best solution to be adopt and why ?

 

Thanks in advance!!