[3DBuff]

Yes 3D switches and plays perfectly, i get frame packed 3D and 1920x1080. But when im not watching any 3D or i set it to play as 2D my resolution will be 3820x2160 no matter how i configure it and the movie will stutter. I just want it to be 1920x1080 even in 2D

I just tested it on my system. There is some kind of glitch, I'm on January release of Kodi MVC.
This could be MVC release or maybe this is in Windows Kodi version.

My understanding is that if you change Kodi resolution inside Kodi using:
Kodi -> Settings -> System -> Display -> Resolution to 1080p then the video will play at this resolution.

It does but it needs a little help.
Set the resolution to 1080p and refresh rate to 23.98. Full screen of course blank other displays ON and Use full screen window OFF.
Now check if the you have 1080p on the TV. If you do try to play video. The trick is not to change the video mode in any way like resolution or refresh rate.
If you get 4K on the TV and Kodi desktop shows 1080p then try to trigger video reset using "Use Full Screen Window" ON and OFF again. Test TV resolution. Once you see 1080p at 23.98 you should be able to play video and keep 1080p without Windows / Kodi converting to 4K.

It worked for me

I also noticed something strange during this experiment on my LG E6. When I got 1080p video going the screen looked different than 4K, picture mode changed and it didn't have typical 24 hard coded frame rate. The TV was still in PC labeled input but the functionality have changed and allowed for image processing like frame interpolation (LG TruMotion). Those functions are disabled on PC input and 4K resolution.