1. Does USB-C to HDMI support VRR/FreeSync/G-Sync?
This USB-C to HDMI Adapter does not support VRR, FreeSync, or G-Sync.
2. Does the Cable Matters USB-C to HDMI 2.1 Adapter support 144Hz?
Yes. The Cable Matters USB-C to HDMI Adapter supports up to 4K@144hz. This requires a USB-C source equipped with DP 1.4 via DP Alt Mode and DSC, along with an HDMI 2.1 monitor.