In 2017 I got my first iPP 12.9, and my idea was that it would replace my Air 2. I wanted it for working (I tutor prospective law students, mostly online) because I was all about getting an Apple Pencil and using that instead of a Wacom tablet with my MBP. I ended up really liking having two iPads and actually never used my MBP anymore. I ended up selling the MBP and went 2-ipad setup only (no laptop or desktop) for a couple years, and eventually I upgraded to 2018 in both the 11 and 12.9.
About a year ago, I decided to get a Mac mini because I wanted to be able to have more reference documents up side by side while teaching. I use the 11 inch in sidecar and still draw on the 12.9 for my online whiteboard several hours per day. I also use the 11 for throwing in my purse when I'm out and about. But in my house, the 12.9 gets the vast majority of the love. I play Civ VI on it obsessively and love the screen size. I don't find it cumbersome.