You can turn off the multiple windows in Settings > Multitasking, reverting the iPad to a one-app-at-a-time mode.
I'm not sure what you mean by the drop down part. Pulling down from the very top center take you to the notification screen in iPadOS 26. Pulling down from below the edge gets you Siri Search; but only from a Home Screen.
In iPadOS27 Beta it opens a Siri dialog both from the top edge and the middle (if on a Home Screen) . The notification center pulls down from the left top. You can turn off Siri to go back to the 26 way, but you lose most of the benefits of the new version. Siri is actually useful in iPadOS27.