Disable and delete Messages on single iPad

I have two old iPads that my family shares for home automation and to watch videos at the gym; one runs iOS 14.4.2 the other 12.4.9. I don’t need most of the core iOS apps to use it.

How do I turn off Messages and delete them only on these two single devices? I’ve turned Messages off in the iCloud settings and in the Messages settings, but my messages remain on the devices AND they new messages continue to appear despite my having turned them off in the settings.

Apple support articles are confusing because they talk about turning settings off on my iPhone instead of my iPads. They also are unclear about whether deleting messages that appear on these devices that still receive and display Messages when the app is supposedly turned off will also delete them in iCloud and my other devices — my iPhone and the iPad Pro I use for work.

Any guidance you can provide is greatly appreciated, as I’m baffled as to why turning off an app and its backup, as well as logging out of Messages and FaceTime doesn’t remove the messages from my the local app and also stop receiving new messages.

Thank you.

Tom