First of all those who says that " my tv is calibrated " it is only for outside game-mode you can't adjust white balance on game-mode to calibrate.
Games are created in 100% DCI-P3 which means you should select the most expanded color space on your TV to see all colors.
And definitely you have to keep contrast enhancer high hence game-mode outputs unprocessed image looks dull/dim, keeping contrast enhancer HIGH gives a hand to highlight details like processed picture
For HDR, DCI-P3 inside the container of BT2020 color gamut which is the most expanded color space.
Apart from all, samsungs native color space is higher than any other color space you have it on your tv so it can easily reproduce whatever the input is even if it is BT2020. That is the reason samsung forces native on both sdr and hdr game-mode.
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