Pixel format changes depending on the resolution with AMD GPU

[cRsFisA]

Hello everyone! 

I have a small problem where the pixel format will change in games depending on the resolution..

For example: I have an RX 480 4GB and I can't run the latest games out at 1080p 60fps so I turn down my resolution. The problem when I do that is the fact that my pixel format changes for some reason.. from LIMITED RGB to FULL RGB (which makes the games look too dark for me). The games stay in LIMITED RGB only if I'm running at 1080p resolution but if I try to go lower they use FULL RGB and I really don't understand why they do that.

My monitor is an Acer Nitro VG220QBMIIX 1080p 75Hz and I'm using HDMI.

In the picture you can see my  default settings.

Thanks in advance!