I don't recommend either honestly as I've switched the S23 Ultra and can't remember the last time I was so happy with a device (I don't even miss root) but if you're dead set on those two, the OnePlus 9 Pro is the way to go. The Qualcomm X60 modem runs circles around the Pixel 7 Pro's Shannon 5300 in the efficiency and stability department and the Snapdragon 888 is marginally faster but runs cooler than the Pixel 7 Pro's Tensor G2. Also, you can unbrick the OnePlus 9 Pro (make sure you back up all the partitions before you start tinkering just in case but if you have the partitions backed up, as long as you don't lock the bootloader, you can generally recover pretty easily) while you can't unbrick a Pixel if you manage to brick it. I chose not to flash custom ROMs on my Pixel since the stock software was good enough and there were a few scattered reports of bricks here and there.
Also, if you check the OnePlus 11 forum, it was discovered that the Battery app is what is in charge of the gaming throttling. There is a thread there about modifying the functionality so it doesn't throttle so soon.
So finally after searching for sometime i got this magisk module which removes thermal throttling for OnePlus 11 1.) First two images - 3D wildlife extreme test without any thermal removal 2.) Rest images - Are after flashing thermal zip
I used it on my OnePlus 9 and can confirm it didn't throttle but the battery temp was quite hot. I was running 3DMark on stress test mode though.
There are 19 ROMs that I know of, they're just not really talked about here since the devs moved elsewhere.