Me headset is the Arctis 7 from Steelseries. It uses 40mm drivers, and its headband seems considerably thinner than that of the Lucidsound LS20. The reason I consider the earbuds is because some games aren't about spatial/great audio. Keep Talking and Nobody Explodes is about taking directions from the other person, and that is tough with headphones on, be it a traditional set or the built-in ones you find on a Rift for the Samsung WMR device. However, in-game audio isn't that important as a whole, so using one earbud from a set of earphones lets you hear the necessary in-game sound while having an ear free for following direction from your playing partner.
Not sure what stops someone from using the demo/preview though. Isn't it just a Steam utility you download? Or is there an enrollment program you have to be a part of? If the latter, what stops you from signing up for it?