A 2-vol strangle (str) is simply a Strangle where the market volatility of each of the two OTM strikes is displayed individually.
The regular strangle, as quoted in the market, quotes a single volatility. This single volatility gives the same price as the 2-vol strangle.
Pricing a 2-vol strangle in SDX Commodities & Energy
When pricing a strangle note the following:
You can only enter it automatically in the Single Option page. To price a 2-vol strangle in the Portfolio page, you need to build it manually out of its individual components.