KORD doesn't have any performance problems. In fact, KORD V2 has an exceptionally good fps, considering how much more detailed is compared to the old one. Here's proof, we took these two screenshots using a saved situation, under exactly the same settings, to compare the old KORD to the new one:
This is the OLD FSDT KORD, a scenery originally made in 2008, which is about 4-5 times LESS detailed:
http://www.fsdreamteam.com/images/2019-8-22_11-53-15-619.jpgThis is the NEW FSDT KORD V2:
http://www.fsdreamteam.com/images/2019-8-22_12-3-1-998.jpgThe resolution it's 4K, the viewing angle is the worse possible, with the whole airport in sight and the Chicago downtown in the background, and every other setting is EXACTLY the same, AI is UT Live at 50%, which still is a lot of planes, and it's a setting that gives you a chance to find some free parking spots, and nothing else is changed, just the scenery.
So no, KORD doesn't any issues with performances. However, it's a scenery that requires A LOT of VRAM, and this is of course have been explained in the manual, with some tips to help understanding which settings affect fps the most.
The issue is, when VRAM is close to exhaustion ( anything higher than 85% ), the sim, and the video driver itself will start to swap textures in and out from RAM to VRAM, and this is VERY slow, because they have to pass through the PCI bottleneck.
So, your goal is to keep your setting in a way that your VRAM usage is not higher then 80-85% of the overall memory you have. For example, to use 4K textures you need AT LEAST 8GB or VRAM and, if you have airplanes with high res textures, lots of AI and high settings, that might not be enough.
Use the default Windows performance monitor, and check how much VRAM you have left. If it's higher than 90%, lower your settings.