You can use Split View and Slide Over with Horizon Client on any iPad model that supports these features and is running iOS 9 or later.
With Split View and Slide Over, you can open Horizon Client and another app at the same time. You can run Horizon Client as the primary or secondary app.
If you rotate the device or slide the vertical divider that separates the primary and secondary apps, Horizon Client adjusts to fit the size of the window. If you are connected to a remote desktop and the Resolution setting is set to Auto - Fit, the remote desktop adjusts to fit the size of the window. For information about setting the resolution, see Changing the Display Resolution Setting.
Horizon Client does not support Picture in Picture.