Question about Microsoft Xbox One X

Without a 4K TV, you get downsampling to HD, just like with the PS4 Pro. HDMI is basically backwards compatible and the console recognises when no 4K or even HDR-capable TV is connected.

HDMI 2.0 is sufficient for 4K, because HDMI 2.1 has not yet arrived on the market, but it has already been confirmed that the Xbox One X will be able to support HDMI 2.1 via an update. So you will get a 4K signal via HDMI 2.0 without any problems, of course if your TV is capable of 4K. Otherwise, the picture will be downsampled to FullHD and will simply look nicer than from a normal Xbox One.