iGPU performance is primary constrainedby RAM bandwidth. I believe your laptop has DDR4-2666 or LPDDR3-2133 (it's bad) max. This X1 Carbon has LPDDR4X so at least 3200 or 4266 best, it makes significant improvement. Intel also improved Xe GPU core. Is it enough for 4K on your use case is different story.

Edit: AT argues that X1C uses LPDDR4X-4267, looks great.

https://www.anandtech.com/show/16392/ces-2021-lenovo-thinkpa...