Is the S85HA a QD-OLED or a regular OLED?

It is a regular OLED (WOLED) panel, not Samsung's QD-OLED. That means slightly lower brightness and color volume than the S90 and S95 lines, but the same perfect blacks.

Is 83 inches too big for an average room?

For a typical living room, yes. An 83-inch screen needs a viewing distance of roughly 8 to 10 feet to feel comfortable, so it suits large rooms or dedicated theater spaces.

Does it support Dolby Vision?

No. Samsung TVs support HDR10 and HLG but not Dolby Vision, so Dolby Vision content plays in HDR10 instead. Competing OLED brands do support Dolby Vision.

Is it good for gaming?

Yes. It has HDMI 2.1 inputs, variable refresh rate and low input lag, so it works well with PS5 and Xbox Series X. The OLED panel also gives fast pixel response with little motion blur.

Should I worry about burn-in?

Burn-in is possible on any OLED with static logos, tickers or HUDs shown for long periods. Vary content and use the TV's pixel-shift and screen-saver features to reduce the risk.