Only expensive capture cards (e.g., Elgato HD60 X, ~$200) support 120Hz pass-through. Most cheap cards limit to 60Hz.
The Short Answer No, you cannot simply plug an Xbox directly into a laptop’s HDMI port and play. Most laptop HDMI ports are output-only , meaning they send video out to a monitor or TV, not in from an external device like an Xbox. plug xbox into laptop
No. But streaming via capture card may use more CPU/GPU than normal. Only expensive capture cards (e