Keep your screen brightness down, but keep it at a comfortable viewing percentage.
Use Dark mode whenever possible to turn off pixels and also save on battery and help improve device performance.
Dark mode can be invoke from the iOS/iPadOS Control Centre, by being on any Home screen and swiping a finger downward from the upper right hand corner od the iPads screen and tapping the icon of a circle that ie filled in half black/half white or can be turned ON/OFF or put on a timer, from the Settings app under Display and Brightness panel, under Options.
Go to the Settings app, under the General Settings Panel and under Background App Refresh, and either toggle this OFF “globally” for the entire iPad
OR
Toggle off Background App Refresh, individually, for any apps that you feel really do not need to have their data always refreshed in the background.
In Settings app, under Notifications, completely toggle off Notifications for any app/s that you feel you do not need notifications for OR modify the methods of notifications to minimise the different Notification delivery method/s.
Also, in Settings app, under Mail, Accounts, Fetch New Mail, modify the frequency at which you autimatically receive new emails.
Make sure the iOS background app switcher does NOT have a “truck full” of apps just hanging out there.
Either dbl-click the Home button or, from the Home screen, slide a finger upward from the bottom edge of the iPad's screen to about 1/3 the way up the screen to invoke the iPadOS background app switcher.
To quit apps, put a finger on a app window and slide the app window, with your finger all the way upward toward the top of the iPad's screen.
You can use multiple fingers to slide up multiple app windows to quit multiple apps.
All of this should help with both overall device performance AND battery life performance.
Best of Luck to You!