About the notification panel, it looks good to me.
About the vibration in Camera, try turning it off in Camera settings. If you can't see it, it's not available in One UI Core.
About the dark background in the All apps screen, turn off Dark mode.
About the keyboard and browser, try restarting your phone. If it didn't work, try going into Safe mode. If it still didn't work, try wipe cache partition.
What browser are you using?
You can not only downgrade your phone back to One UI 3.1 (Android 11) by going to the repair shop, you can downgrade it yourself using Odin in your PC.
Although for scrolling, you can check the first comment as your guide to eliminate the animation. As well as for the notification display and brightness customization.
We value your comments and feedback here. Hope our dear Samsung members were able to satisfy your query but if not, allow me to assist you by providing you with the vast array of support links that you may select and use in order to enhance your user experience.
One UI 4 Key Features and Enhancements.
Samsung support channels.
Samsung Service Center
If the problem persists, I highly recommend that you bring your Samsung Galaxy device to only Samsung Authorized Service Center near you.
Hope this content helpful and your problem gets solved.