I have the exact same phone, and have the exact same issues. I hate the update. The stutters dissappear when you drop the resolution to 720p but I'm NOT going to use a 6.7" screen on a 720p resolution. Cmon Samsung, this is ridiculous. One more awful thing they did is make the share menu same as iOS - horizontal.Received OTA Android 12 with oneUI 4.0 yesterday. I'm very disappointed with this update! There is very noticable stutter while using the navigation gestures, especially the one that lifts the current app up and shows the app switcher. Also there is terrible stutter while scrolling between the quick toggle pages in the notification shade. There are some other stutters here and there, but those are the most noticable. It's like Samsung forgot to optimize some parts of the UI. The stupidest thing is that with Android 11 my phone was perfectly smooth. It's an Exynos s20+. I thought that the TouchWiz days are long gone, but...
I do not recommend this update. It's not like the phone is slow, I would say it's a bit faster, but there are noticable frame drops through out the UI.
I'm going back to Android 11, it worked perfectly for me.