Haven't tried specifically but even if set the Deck will still be both power and to a lesser extent thermally limited. The APU itself has a max TDP (without tweaks) of 15w which must be shared between the CPU and GPU. Assuming you could lock the GPU clocks at 1600Mhz* the CPU will not be able to boost as hard as it would do if the GPU clocks were lower - same power budget.
* Even if set I imagine the GPU will just do its own thing with the max available clock being 1600. This is the same as AMD desktop / laptop dGPU's. You can tell them to run at say 2500Mhz, but the actual boost clock will be lower due to all manner of different reasons.
I did see on the Deck Reddit that some people have been running the Deck at a higher APU TDP (not looked into this further than just reading the comments so can't confirm validity), but then noted it just hit the thermal limit instead.
On the separate note of the new Windows APU driver, I tried it last night on my SD Win 11 install and so far, the performance seems markedly improved in Destiny 2. Framerate itself hasn't shot up or anything (capped at 60 to prevent tearing), but it feels way more consistent with less drops into the 30's. Essentially it is no longer a stuttery mess in areas it was previously a stuttery mess.
Will try my other Windows install (docked with USB SSD) either tonight or tomorrow. I am most interested to see how the performance is like at up to 1080p.