Amending/deleting Notes or Calendar entries on iPad or in iCloud
If you are signed into iCloud on your iPad, generally changes you make to iCloud-synced items will sync to your other devices through iCloud.

Particularly for Notes, you can have device-specific notes by doing the following on your iPad:

Go to Settings > Notes and go to the bottom where you should see an "On My iPad" Account option. Toggle that on and you will then have a place in Notes to store notes that stay just on your iPad. This will appear in the list of folders under "ON MY IPAD" and you can create new folders under that section, just as you would for iCloud.

For Calendars, there is no way to maintain a local-only calendar and still sync another calendar to iCloud. (You can do this if you use something other than iCloud to sync your calendar, such as Gmail, but not with iCloud.)