The Pro version has "Dual Layer Target Size" in the 'Settings' menu.
Yes you still have to re-encode if you're trying to convert to anamorphic.
If your target size is DVD-9, DVDrb may not turn on the encoder because it feels there is enough space.
If that's the case then you have to go to the 'Mode' menu and select "Force Reencoding (For Filters)".