Apple Pencil support would be super cool on the iPads. Also worth noting, aside from typical handwriting inputs like Wacom digitizers, found in laptops like Lenovo's Tablet lineup, the MSoft Surfaces, etc, Wacom also makes pen tablets at a price point of less than $100USD, although they may be a little different to write on as they are just digitizers, and you'd be watching the screen to see what you're writing. Works great for art though!

Didn't Microsoft introduce some kind of collaborative OneNote-like program that also does recognition of common symbols (arrows, boxes, etc?). Similar to Google's Jamboard software? I thought I remembered seeing this in one of their Surface presentations but can't seem to find it now.

There's an application on the windows store called Nebo that does writing and write recognition and claims to do drawing recognition too (although I rarely use it; I wanted to use it for math but that is extremely dodgy so far; not sure why because detextify would give it ample training data).

It does have an option for graph paper instead if lined. It's not engineering graph paper with the darker and lighter lines, but still better than lined or blank paper.

You can also set the pen to snap to the grid on the graph paper that makes drawing quick block diagrams really easy.

The word write is pretty generic.