The second drive is for your pocket, and the X10 sports an IP65 resistance rating so it won’t suffer for the experience. The X10 also uses a Silicon Motion controller, this one being the SM2322 and uses a USB 3.2 Gen-2 2×2 connection. That does mean you will need USB-C on both ends to see the peak transfer speeds of to 2.1GB/s sequential reads, which happens to be almost exactly twice the bandwidth of the previous X10. It is also more than enough to record UHD video or even carry your Steam library around with you so you can play anywhere. It will work on just about anything, Windows, Mac, Android, iPad, PC, Linux compatibility covers everything but your game console.
The X10 will be shipping in 4TB, 6TB and 8TB models so you will indeed be able to fit that Steam library on there, along with just about anything else you might want. It could also make a handy extra backup of your system; the more you have the more likely you’ll have a working backup when you need it!