Click the battery icon in the taskbar.

Use NVIDIA GeForce Experience or AMD Software.

Laptops throttle performance on battery.

Use Task Manager to kill Chrome or Discord. If you want me to tailor this further, let me know: What specific game are you playing? What are your laptop specs (GPU/RAM)? Are you experiencing stuttering or just low average FPS ? I can provide a step-by-step guide for your exact hardware.

These eat CPU cycles.