The all the way open thing is so real. Most drawings only show the fridge box size and nothing about door swing, and then you move in and realize you can't open the door past 45 degrees without hitting a wall or the island. We ended up going with a counter depth fridge partly for that reason. And to answer your question, I made the cardboard top exactly counter height, not lower. Because if you make it lower you trick yourself into thinking it feels fine when it really doesn't. You want the fake counter to match what you'll actually build so your body gives you honest feedback. Standing at a too low counter for 10 minutes is a whole different feeling than standing at one for an hour while you're cooking.

My buddy had the exact same thing happen with sugar cookies, kept texting me pics of these sad flat blobs asking what he did wrong. Told him to chill the dough and he acted like I was messing with him, then came back a day later like "ok you were right." Cold dough really is the whole game, it stops the butter from melting before the cookies can set up.