Any tips on fine tuning the tv settings for ED on the Xbox one x? Always seems so dark. I’m rocking a 55 inch Sony 900E
The answer is going to be, unfortunately, "it depends." Every TV is different and even every individual unit of the same TV model is different. Have you ever calibrated your TV? The tool included with the Xbox One X would at least be a start. From there depending on your level of commitment (and available funds!) you can get a self-calibration tool like a Spyder or you can pay a couple hundred for a pro to do it.
Anywho, you ought to calibrate first, then make in-game adjustments as needed. I would not suggest adjusting the TV's calibration settings to suit the game, adjust the game's settings to suit your desired result. If it's too dark (after calibration), boost the gamma of the game.
Do you have the 4K and HDR working correctly? I had to go through a couple of hoops to get the X to correctly recognize the UHD-ness of TV through my AVR, but once it's working it's glorious. Get that working first, then calibrate, then nudge the game settings if you need.