If you’re going to use the iPad as a whiteboard then I recommend getting the largest one. I’ve used both that and the regular one — in my experience the regular one is just too small.
It looks like we have consensus that basic ipads together with Apple pencils are the way to go. I use it together with Good Notes to share ipad screen through my laptop. But it works with zoom directly too and you can integrate it with Box. So I will go ahead and order couple of sets to test drive during the summer.