How does speaker placement affect the width of the soundstage?

If you go to the Cardas cable website they have a speaker setup guide .

myself i wider speakers then just toe the in a little and they have a big soundstage .

what type of tweeter you have ,and if it’s in a wave guide better still.

In addition to/in conjunction with speaker placement, the acoustics of the room have a major influence on soundstage.

Of course speaker placement is everything to soundstage but without seeing a picture of your room layout, it is impossible to pinpoint your shortcomings. 

I am no expert but I can offer that in my room toeing in the speakers more reduces the width of the soundstage and re-enforces the center image.  Just the opposite with toeing out the speakers.  I prefer a more toed out positioning but not so much that I lose the center image. I think many people have too much toe in on the speakers.  Depends on room too.  Also, small adjustment in angle, like an inch, can make a big difference.  This was surprising to me.  

+1 @baylinor  The room is critical. Hard to help without knowing the layout and room contents.  I think of the room as another piece of equipment.