Regarding external display support on iPadOS 26, a few annoyances:
The dock is hidden when apps take up the full height of the display. This leaves no straightforward way to open apps on the external display. The best you can do is (1) open the app on the iPad, (2) right click the traffic lights, (3) select “Move to [External] Display”
There is no way for the menu bar to always see visible, either on the external display, or on the iPad. So to view the menu bar, you have to do a click-and-drag-down gesture from the top of the screen.
The display scaling on a 4K monitor is terrible. Websites are obscenely oversized. They do not render like Safari on Mac at all.
The whole system has a very slight input lag. Typing characters, clicking the mouse, feels like it has a 50 to 100 ms delay to it, that doesn’t exist on macOS. It makes typing slightly challenging.
Moving and resizing windows on the external display is very imprecise. It’s like moving jello. Like, the windows are slow to move, and it’s very unpredictable where they’ll land up.
The windowing system on the external display resembles macOS, but window manipulation on macOS is still far superior than it is on the iPad. Even on the external display, with a mouse and keyboard, iPadOS 26 has the most challenging window manipulation I’ve seen of any operating system, and it hasn’t really improved since iPadOS 18. I’d use an external display with the iPad as a last resort, but this shouldn’t be the primary means of using the iPad.
This system resembles macOS in the most superficial way, but I cannot emphasize enough that this user experience is nothing like using a Mac desktop.