Is the RU800D good for gaming?

Yes. The 120Hz native panel and low input lag in Game Mode make it a good match for consoles. It lacks HDMI 2.1, so 4K at 120Hz is not supported.

Does it support Dolby Vision?

No. It supports HDR10 and HLG but not Dolby Vision, which is common for Samsung TVs.

How does it compare with Samsung's QLED sets?

QLED models use quantum dots and full-array or better local dimming, giving deeper blacks and wider color. The RU800D is edge-lit and sits a tier below.

Does it have local dimming?

It has only limited edge-lit dimming, so contrast in dark scenes is weaker than on full-array sets.

The TV, its stand, a remote and power cable. A wall mount is not included.

Is 75 inches right for my room?

For a typical seating distance of about 9 to 12 feet, 75 inches works well for mixed viewing. Closer seating makes standard-definition content look softer.