Medieval 2 total war Poor Performance help

[TribuneSPQR]

Hi, I can manage a 1v1 battle with maxed setting with good performance, but when a third army is involved the performance is horrid, camera/units lag. I even turned shadows off, bloom off, grass off, and units low and no improvement. Mega frustrated cus i really want to play the third age mod with great performance and battles.
Specs -

i5 3570k OC

Sabertooth motherboard
GTX TITAN

All drivers are up to date pc is very clean so they are not the cause of it. My medieval 2 game is on steam so i do not have the option of compatibility mod in properties (heard this does not work anyway)

Would really appreciate anyone who know how to fix or any possible help.

[Aeratus]

Sounds like something is causing your CPU to bottleneck. Try this: go to windows task manager, and compare the CPU usage for 1v1 and for 1v2, and see if there is a difference. If the CPU usage is lower for 1v2, then you know that something is causing your CPU process to be de-optimized.

Also, try turning off the CPU's OC. With old game engines, OC can cause some unintended bugs that could de-optimize the CPU.

Also, did you install any mods that affect the game's battle AI?