As far as I know the main problem with ARMA 3 engine is this;
1 - it still has a lot of code from like 10 years ago
2 - that code was written before multicore processors developed, and the code was specifically written for single core processing systems
3 - that code has never been rewritten or maybe can't be rewritten
From what I've heard the main thing that helps with ARMA multiplayer performance is having a processor which performs well with single thread processes.
So check this;https://www.cpubenchmark.net/singleThread.html
It is highly unlikely you will find a lasting solution to a problem if you do not adequately comprehend the origin of that problem.
"an appeaser is someone who feeds a crocodile hoping that he will be eaten last"