Using iPad for a single app (full time)

Does anyone else use a (usually older) iPad for one app full time? If so, I was wondering if anyone has any tips or tricks for setting it up.

My example:
iPad-3 with PoE camera running Amcrest Surveillance Camera View-Pro for iPad
iPad-5 running Harmony Remote (in iPort LaunchPort Dock)

Other apps include Roomie/Simple-Control, Ring, Eufy Security and Home Automation Dashboard.

The problem/question is: Keep iPad logged in to iCloud?
The obvious cons are notifications popping up and random users potentially gaining access to our private stuff.

Sure, you can use guided mode, but I don’t think that will stop the notifications.

So I’m using a personal iCloud account here, but sharing an Apple-ID for iTunes/App-Store purchases. This is how we did “Family Sharing” before Apple made the rules. You can still do it during the initial setup…so I do (well…because it works). So now I can sign out of iCloud (remove access) but still be able to use the App-Store and even update some apps I have installed on this particular iDevice. I’ll try it right away.

So let’s say you don’t do it. Use only one Apple-ID for everything (App-Store purchases and iCloud).
I think this means that even deleting an Apple-ID is not possible.
I usually have all iCloud options enabled on the iDevices I use on a daily basis (except iMessage… I don’t want it in the cloud, I only want it on my iPhone).
So, on this one iPad, can I turn off the iCloud options for Contacts, Notes, Reminders, etc. and not create any local content at all?
I think another scenario like this is when your main app needs to use iCloud-Drive storage or other iCloud resources.

Anyway, I’m wondering how to handle this and I hope we can discuss it.