And... you want it to be an iMac? As someone who actually tried that, I'd suggest that maybe your expectations are a wee bit unrealistic -- either that, or perhaps you're undervaluing your other non-gaming priorities.
When I bought my iMac, I actually cancelled the first order I'd made and reordered it with the highest end graphics card that they offered for that machine. I absolutely did not regret that decision; it truly is a great Mac and when booted into Windows, made a halfway decent gaming computer. But -- and let's just be real here -- anyone and everyone who was into PC gaming would (at best) politely chuckle at me when I told them that my "gaming" computer was an iMac. It couldn't hold a candle to their real gaming computers, which (on the two extremes) were either half the cost of my iMac at comparable specs or were twice as fast at the same price.
Mind you, I've owned three different iMacs over the years (2006/2012/2019) and still absolutely love my current one -- and I'm of the very firm opinion that the sweet spot was and always will be that gorgeous 5K 27" display. But these days, the iMac stays booted comfortably into macOS, while a gaming laptop compliments it by picking up my Windows activities: a three-year-old laptop with an nVidia 3070. It does... okay... for what it is.
But that 27" iMac -- while it was never a true gaming computer -- absolutely was the best value you could get, for the unique niche that it filled. At least... for a time. I honestly doubt that Apple will be able to catch that lightning in a bottle all over again.