Is the 48-inch S90H good for gaming?

Yes. It has low input lag and supports high refresh rates with variable refresh rate, which suits consoles and PCs. OLED motion is clean, though static HUD elements are worth watching over long sessions.

How does it compare with Samsung's mini-LED TVs?

OLED wins on black level, contrast and viewing angles. Mini-LED sets get brighter, so they handle a sunlit room better. In a dim room the S90H looks the more cinematic of the two.

Is 48 inches big enough for a living room?

It suits a small room or a viewing distance of roughly 5 to 7 feet. For a large room with seating far back, a 55-inch or larger set fills the view better.

Does it support 4K at 120Hz?

Yes, it handles 4K at up to 120Hz on compatible HDMI inputs, which covers current consoles and most gaming PCs. Check that your cable and source device support the full bandwidth.

Should I worry about OLED burn-in?

Burn-in is possible with static content left on for long periods, such as a news ticker or a paused game. Normal mixed viewing is low risk, and the TV includes screen-care features to reduce it.