I use the Wulff Ambush line on my 11ft 4wt and 11'9" 4wt two handed rods.

It is not really a Triangle Taper but more of a level Skagit type line that works well with 10ft sinking leaders.

A much better line for light spey rods and longer single handed rods is the Airflo 40+.
The 40+ has a long taper similar to the Delta taper and performs very nicely with all of the classic spey casts.

The commercial video is not very clear on single handed spey casting.
To learn the casting techniques, a good reference is the new book by Simon Gawesworth, Single Handed Spey Casting.

Regards,
FK