Only just got my DK2, and I'm not sure I've optimised it yet, but here's my experience so far. Running on an NVidia 970 and an old(ish) i5 cpu, 12Mb RAM. I started off with the latest NVidia drivers, which would only allow me to run in direct mode. I got juddering and freezing when I moved my head, especially in asteroid fields. So, I rolled back to the last set of drivers and went for extended mode.
Huge improvement, no more freezing and juddering. Still get the odd hiccup when graphic detail changes in supercruise - like when you approach a planet or similar and it jumps to a new level of texture detail. I'm sure this is nothing to do with the OR though. I'm still using the default orange HUD so far, I find it not too bad to read, especially if you lean in a bit. If the devs don't implement an option to change soon I may give green a try just to see how much of an improvement it is.
@MACMAN yes it's only for the Rift, unless you use mulitiple monitors. But what people are referring to here is specifically a Rift setting.
But anyway, to the OP, I don't have a monumentally strong rig but I get very little judder. Everything is set to Ultra/High. I'm flying combat almost constantly in asteroid fields and it's very smooth. The only occasional hiccups are gfx loading induced as mentioned above. The only thing I can find to criticise about the DK2 so far is the screen door effect, which is a bit distracting but I'm happy to live with it til CV1 arrives.
Long story short - direct mode bad, extended mode good.