Change 1440p to 1080p and your usage of the cpu becomes higher. How wonderful!
If you don't have above 94% of Gpu usage, you could change 1440p to 4k. I guarantee it will get up.. And guess what.. Your cpu usage will go down with a 3090.
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If I had a 3090, I would use it to play in 4k. I am still waiting on my 3080, will play on my 4k TV.