I've bunged an Ubuntu partition on it which takes up 150gb, which I'll use for everything but a little bit of gaming, have installed FM and Civ on the Windows partition, and am down below 200gb already.Mine isn't due to ship until 31st August lol.
From what I can see on YouTube, it should have both a 2242 slot and a 2280 slot.
Ps why do you need to fill both? 512gb not enough?
The reality is that 512 should be more than enough for me and I've probably made my Ubuntu partition a bit too big, but a second SSD for £50 or so, which would allow me to completely hive Ubuntu off onto another drive, would be nice.