You can really go either way with Targas or 390s for that setup and type of riding. The 390s are more of a mid-flexing binding that will be awesome for free riding and in the park. Many people use them for riding pretty much all types of terrain.
The Targas are going to be stiffer and more responsive, but you get the added option of being able to change the stiffness of the ankle strap with 2 different inserts. You get a stiff flex, medium flex, and then you can run it without any insert at all for the softest flex.
If you're primarily riding in the back country and enjoy some good response, you may prefer the Targas if you'll only be in the park some of the times. It really comes down to preference in terms of flex. For instance, we know of a lot of people that ride the Artifact Rocker, which is a super soft deck, with Targas in the park.
Any other questions feel free to shoot us an email - ridercouncil at romesnowboards dot com