If you're in the USA then don't allow the Android 12 update to install until they fix the VoLTE issues. You literally cannot make or receive phone calls right now.
As for the performance, I never played games on mine, so I can't say what the gaming performance is like. The phone's general performance while using it seems to be better (I'm not needing to activate X Mode when using the Amazon Shopping app to get it to run smoothly, the Steam Chat app connects to the "friends network" and loads conversations fast, and I can actually watch 4K videos in NewPipe without stuttering/buffering), and WiFi performance seems the same or better as with Android 11. 4G performance seems better, but that may also be due to the fact that I have limited 4G bandwidth (due to using a third-party carrier and not the one that owns the network and towers it connects through) and VoLTE is no longer available so it isn't using bandwidth, so I'll have to wait for them to fix the VoLTE issues before I can say for certain if 4G performance is actually better.
I don't like some of the UI changes, such as the huge quick settings buttons in the pulldown menu. Where I used to have 4 quick settings buttons per row in the old pulldown menu, I now only have 2 per row which forced me to rearrange things so the layout of the buttons made some sense this way. I also hate how the WiFi toggle in quick settings was changed to an "Internet" button which now opens a menu when tapped instead of acting as a toggle. They also made the notifications larger while wasting most of that space for padding, so the notifications seem to show less information despite taking up more space.
The settings app also had larger text, and it appears that it reset the "Display Size" to "Large" when updating to Android 12. Setting it back to "Default" feels better for this size screen, but doesn't solve the issue with the wasted space in the quick settings pulldown menu (it just reduces the font size of text). Seriously ASUS, I may be mostly blind, but I wear contact lenses so I can see fine... Hell, I can even see the screen fine without the contact lenses as long as it's within 6 inches of my face, so I don't need gorilla-sized text and UI widgets...
I have yet to delve any deeper than that, however I did notice that the phone has an option for dual band WiFi (I don't remember if it had that option with older versions of Android). I turned it on, and it works just fine. My WiFi signal is stable and fast in the kitchen now, and it wasn't when only connected to my 5 GHz WiFi.
My screen refresh rate and icons all remained the same after the update, so that's good at least.
I can still activate X Mode and the flashlight with the air triggers as I had it configured before the update. The vibration when doing so is different, perhaps a bit stronger, and seems to last slightly longer. It's definitely solid feedback for when you activate those functions by squeezing the air triggers, whereas before you could accidentally activate them and not notice due to the vibration being a bit too light. I did notice that it seems like the force needed to activate these functions via the air triggers may have reset, as it seemed easier than it should have. Granted the only reason I had it set to require a lot of force before was due to the fact that it would sometimes activate when I was just holding or picking up the phone, so we'll see if it starts having that issue again.
Unfortunately I have no clue where my phone's box is, and thus I don't have access to any of the extras and can't test them to see if they still work. I also never used them to begin with, so I couldn't say whether or not they function the same as they did before.
Unlocking the phone with my fingerprint seems pretty responsive. Possible more so than with Android 11. I just tried unlocking the phone about a dozen times in a row, and it took the same amount of time each time (was reasonably fast). With Android 11 I remember the speed and reliability of unlocking with a fingerprint was somewhat flaky, often differing in how well the screen recognized your fingerprint or how quickly it recognized it. Keep in mind that I haven't had Android 12 installed for even an entire day yet, and I don't know for certain how well the phone will react after it's been sitting there idle for hours and I pick it up and try to unlock it.
If there's anything I missed, then let me know, and I'll try to take a look at it for you.