Go OLED if you can, grab a 1tb sdcard for storage expansion. Watch a few people tweak the settings of a game and the graphics card. You can force lower settings and make a game have higher fps and much longer battery life and not really see a loss in graphics due to the smaller screen. Also watch a few tutorials on tweaking steam controller settings. So you can pick up some rando game that's built for kb/m and make it work nice with a controller. Especially gyro, FPS games are more fun being able to gyro the crosshairs a little for micro movements like targeting the head.
Also once you get it, play Aperature Desk Job. It's free, and is a nice 30min tutorial of your deck.