I noticed this was an old thread yet went through it to see the progression of the ppq experience.I just purchased a Walther PPQ M2 sc with tritium sights and I took it to the range and my shot groups were 3" to the left and 1" too low at 10 yards. I shot my Beretta, and was dead center.
Response to your low left shots.
Iagree Walthers sights should start out deadcentered , symmetric to the slide centers on the center line
Check that. If off the center it.
Sand bag test shoot before and after any adjustment.
As this is an sc model you may want to try different backstraps to get a better for you, grip and trigger placement .
Shooting low left for a right handed shooter is frequently a result from placing your trigger finger too close to the tip "too much finger" on the trigger.
combine in pushing the trigger right and upward. This result in pulling shots left and downward .
Why? Because this applis pressure on the trigger off centered at the instant of the trigger break.
The trigger finger moves at an angle relative to the barrel centerline., Not a straight back press. This s pushes the trigger to the right and slightly up. The pistol pivots so the muzzle dips down and left.
This is really common with Glocks , but even 1911s or any handgun will do that too.
Try dry firing with different back straps and trigger finger placement. Untill you get a straight back trigger press and the barrel muzzle remains in-line on target.
Just some tips for consideration.