Can I use 2 Identical iPads?

I bought a new iPad mini-5 and set it up using my old iPad mini-4.

It copied everything including my pictures and notes and apps.

I find that I like having 2 minis. I can be using one and looking up things on the other.

Using a split screen or multitasking on the mini is not satisfactory due to the small screen size.

Is there any reason I can’t keep using both of them?

Will there be a problem to update them to iOS 14.6. If I update one will the other automatically be updated or do I have to update them separately?

Thanks, cb