Question about twf with Shintao

Been doing some theory crafting.
Handwraps are twf,
But twf gives off hand proc

Question is, how does this matter for unarmed?
How does off hand proc matter for a single weapon?
It's not doublestrike, it seems to matter only if using 2 weapons,
For the proc rate on the second weapon, say a vorpal
If you take twf, you get 40% chance when vorpal vorpals that it actually vorpals,
Right?

Reason I'm asking, I'm building an aasimar monk, and trying to fit in completionist
And basically if I lose twf I can make a good build, but if I have to include twf everything is pushed back a level and I lose complete.

Anybody got an answer for this?