Hello
No, you can't change video resolution and frame rate in real-time.
You can just setup maximum values, for example: 640x480, 30 fps, 500000 bps.
WebRTC may automatically adjust these values targeting low-latency.
For example, it can reduce to: 320x240, 20 fps, 300000 bps dynamically.
See chrome://webrtc-internals charts for more information.
Example: