Here is top.... MySQL tends to go way over 100% CPU a lot....... Load tends to be 3 to 4.
Note: The client told me he has installed a php chat, so, I guess this is adding to the strain......... We all know WordStress plugins can be badly coded...
Yeah humm. It would require a lot of data to recommend a server. It might be the server you have isn't powerful enough. Since it is a forum site you might better need to understand concurrent users, applications, file sizes (images) and peak times.
Chat is very intensive process. I have had sites turn that on and cripple the entire server. So you might need to recommend them buy a much more powerful server.
Forums and chat services are not like running a website its very intensive.
However based on The numbers you gave for PHPFPM.
You have total of 32,768 ram to assign to the entire server.
If you could assign all of the ram to PHPFPM max_child would max the box out set at 381 < Setting this would cripple the server.
If we wanted to set half of all the ram to PHPFPM max_child would be 190
If we wanted to set quarter of all the ram to PHPFPM max_child would be 95
If we wanted to set a fifth of all the ram to PHPFPM max_child would be 76
You might consider changing to dynamic instead of ondemand
Here is a good video about how it all works.
Learn how to manage how PHP-FPM creates and uses PHP processes to get the most out of your server.
serversforhackers.com
What does show?
Current active profile: throughput-performance
If this is a dedicated server it should set to throughput-performance
Other things to consider would be moving to MariaDB 10.4 or higher
Using nginx_apache instead of just apache.
Just some more thoughts.