I had to buy several usb c cables on Amazon before finding one that legitimately supported full 4k at 60hz. The first one had a 4k 30hz limit and I had terrible flickering and screen tearing and even something that looked like gpu artifacts. This is the cable I went with

USB C to HDMI Cable 15ft... https://www.amazon.com/dp/B086TV199X?ref=ppx_pop_mob_ap_share