I’ve managed to cleanup all of leftovers and it works! At least partially.
Finally the gpu does not wake up and suspend all the way round if any app wakes it up. After waking up 4070 can sleep properly. Finally the battery lasts for a resonable time and laptop does not heat excesively. Got ~15W usage while writing this post - not as low as you described but definitely better than 35+
What I noticed is that after unplugging external monitor the gpu never even tries to go to sleep again - in that case reboot is necessary to allow it again.
Sometimes after boot it’s looped in constant sleep/wake like before but suspending laptop and waking it up fixes this and then gpu can properly enter D3Cold again.
Also If I suspend laptop and then close the lid - the laptop wakes up for a bit and then turns off. Journalctl reports stacktrace similar to this one 555.58.02-10 nvidia-open driver crash
Could you try to check if above happens also in your case?
I’m using pretty much same config as you Arch + Plasma. I did the testing on 555-dkms and 560-dkms beta from aur combined with linux-zen kernel.