I have that case (but mine came with pmags). It's good enough, the backpack straps are a little cheapy and I can see it not standing up to abuse, but for me it's been solid hauling it to/from the range for a few years now. The dividers in the mag pouches are pretty flimsy. My poverty pony hasn't fallen out or been scratched up.
It will fit a 16" with a fixed A2 rifle length stock, but if you had an 18" or 20" it wouldn't fit without a collapsable stock. Plenty of clearance for optics and bipods and such, but it won't hold two of any size (although you can almost fit a braced pistol in the outer bag, you just have a bit of the brace sticking out).