Safari has been buggy ever since updating to macOS 27 Golden Gate. First of all, whenever I go to make a couple windows split screen (I've noticed with other apps too) by dragging one window over the other, it doesn't reliably work. I'll have to drag and hover repeatedly, sometimes unselect and reselect one of the windows and then finally after a few attempts the split screen will work
Secondly, whenever I drag a tab out of my current window to make it its own window, the top of the screen will glitch, sometimes the whole screen glitches and the window occupies all but the left 1/8th of the screen for whatever reason.. The issue persists in split screen view as well. Screenshot of the first mentioned issue is attached (see how the top on the left window looks strange)