How many workers are enough


We're hosting company and are install to our customer VPS (4 CPU, 8 Gb RAM) with cPanel+LiteSpeed+LiteMage Unlimited

Now when we clicked site it seems that some pages/category pages are coming behind cache very well but some pages not coming with
cache at all. This problem can be also noticed when you refresh some pages ex. if you refresh site then it comes behind cache.

Yesterady we add one worker (essential > professional) and it seems that problem still exists someway and sometimes but I think that things goes better.

My first question is that should we get more workers or might there been something else problem with cache (magento or server side) ?