Correct me if I'm wrong here, but is the 395 not leagues ahead of something like a 4090 when it comes to performance per watt? Here's a comparison graph of a 4090 against the Radeon 8060S, which is the 395's iGPU:
Now that's apparently running at the 395's default TDP of 55W so that includes the CPU power. It's also clear that a 4090 can trounce it on sheer performance when needed. But if we take a look at this next graph:
This shows that a 4090 has a third of the performance while still running at 130W, more than twice the TDP of the entire 395 APU.
Edit: This was buried in the comments under that second graph but here's the points scored per Watt on that benchmark: 130W = 66 / 180W = 85 / 220W = 92 / 270W = 84 / 330W = 74 / 420W = 59 / 460W = 55 and this clearly shows the sweet spot for a 4090 is 220W.