There is a complete “science” (probably close to alchemy or sorcery) on how to do that, and that’s highly dependent on the type of machine, internet line, etc… it’s probably the type of thing you should ask on the Admins United discord, more people with more experience with big servers.
- How can I fix BattleEye constant crashes and normal player crashes when my internet and server resource consumption are normal?
I’ve never heard of BattlEye crashing, do you have some crash reports or crash dumps showing that?
- Are there server settings that allow you to place Altars close to each other.
No idea, it’s a game question, I only deal with launching servers.
- Why is there no difference in Maximum Tick Rate between 120 and 500?
Well, if you put the mouse cursor on the tick rate option, you get a tooltip:
"How often the server processes game information: In an ideal world you would like this value to be as high as possible, but in practice the more players you have, the more NPC are active, the more the CPU cost will be high which will make the sfps to be very irregular\nTLDR: You should probably stick to the default value of 30"
It’s all related: When you increase the tick rate, you increase CPU usage on the entire server, and at some point it does not even have time to do its normal work.
Basically your question is a bit like “My car used to have a limiter that made sure it could not go over 5000 RPM, I removed it so now the engine can go up to 10000 RPM but for some reason now the temperature gauge is going up and I think I just broke the clutch, why is that car not going any faster?”
To improve performance on a server, you need to do things one step at a time, see if things change (for the better), then concentrate on something else.
If you try to tweak everything all at once, you will probably get more frustration than improvement.
Also if the hardware or the internet line is not good enough, you will never manage to handle more than a certain number of players at a time, and if you allow for very large player built things and add many mods, this number of players is going even lower.
- What exactly does the useaviliablecores function affect? Will my server be more productive for the players with it?
It’s difficult to answer because there are so many parameters going on.
Basically Conan Exiles is based on a very old version of the Unreal Engine, which is not particularly designed to use many CPUs, it’s mostly “single threaded”. That being said, there is some support for doing things on the side, mostly small tasks and things like loading data from disk for example.
In practice, it’s better to have a fast CPU without many cores than a server monster with many cores running slower, but you can still play with these options to help improve things.
Personally what I do is to leave the first core for the operating system, and I use the check boxes starting from the end of the list to indicate that the server should have “affinity” with these. The server itself does not know about it, but this system basically informs Windows that when the server tries to create threads it should try to use these cores instead of the default ones, so that helps a bit with the server and Windows not fighting with each other.
That also helps when running two servers on a big server: You can give each server their own set of cores.
The useallavailablecores is a flag provided to the Unreal Engine that changes the number of threads the server creates, that may help having a few more things happening together (more threads), but don’t expect miracles.
Good luck 
