When I was looking for crates (ended up not getting one), I found a few wire crates that were adjustable. If I remember right, I found them at Amazon, but I don’t remember the brand. The reviews were so-so.
Our house has an open floor plan too – there’s only one door on the main floor and that’s for a small bathroom. Our puppy found a place – next to whichever human is closest. Her second favorite place is on the upstairs landing, where she can keep an eye on everyone. Apparently she feels safe anywhere.
Yeah, you generally block off the end of the crate. The idea is to get a crate that isn’t SO big the dog is comfortable soiling it.
But in this case the crate isn’t (apparently) being used for housetraining, just more as an enclosed dog bed. Wouldn’t worry about the size. The dog may, however, not use it - depending on the dog. Dogs who prefer their crates for alone time have often been crate trained to prefer their crates.