10 degrees or 0. Use the Square grind semi-skip chain. This is set up for 10 out of the factory. No need to grind a new angle out of the box - just remove about every 6th top SIDE of the cutter (just leave it about 1.5mm wide. When it comes back for sharpening, grind to 10 round, or 0.
Getting a "best performance" ripping chain is more art than science - depends on the wood type, grain structure of the tree, and the power of the saw. Might need more or less cutter sides removed. The one I described works well in on the NW softwoods, even though some heart Doug fir is amazingly hard!