A:AnswerYes, this machine supports an additional 2.5" storage drive. https://dlcdnets.asus.com/pub/ASUS/GamingNB/FA506IH/E16601_FA506_FA706_Upgrade_Guide_V2_WEB.pdf
A:AnswerI Use a Dell Universal Dock D6000 for mine. You can use the USB-C or USB A connector (Dock comes with adapter) . No issues at all with it. That dock in particular works with many laptops that have at least a USB3-A.
A:AnswerI just received this laptop in the mail - I can tell you 100% that it's fully plastic - top plate, keyboard, keys, everything. I'm not saying it's bad or poor construction, in fact it seems to be constructed quite nicely and I'm happy with it. But it is all plastic. The screen lid is made to look like aluminum as it's a shiny grey look, but it's definitely plastic. The plastic around the keyboard around is made to look like brushed gunmetal steel, but it's plastic. I do really like the look of the brushed steel, though.