The first HDMI 2.1 cable we have, it's the latest HDMI standard. So do you have a TV that can deliver 8k or 10k? Then it's an HDMI 2.1 cable you need to grab.
USB-C to HDMI is an adapter that allows you to connect your Macbook with USB type C to an external monitor. The adapter is made eg to put your TV or external monitor to your Mac, it requires an HDMI cable. The adapter supports 4k at 30Hz, but also e.g. 1440p at 1440Hz or 1080p at even more Hz.