It's very difficult to compare boards from different brands, as this is subjective and our technology is different. When one speaks about stiffness, one has to distinguish longitudinal stiffness and torsional stiffness. Moreover static measurements at home can't be totally compared to dynamic behavior on the snow. This is really a science.
That's why we organized 34 events since 2004 to:
1) let people test the flexes and board sizes to find what matches them the best (95% of the time they confirm our charts)
2) give advices and informal lessons on the snow to teach our ride technique (and setup) which suits well our wide alpine boards; we noted that the problem of "dead legs" after a few runs often comes from a bad timing in the push-pull technique...
There are 1000 things to tell/show, and the best is to do it on the snow.
That said, we are quite confident that the 175H will be comfortable for you (weight 105 kg). Swoard boards are known to be not too stiff longitudinally, so the flex of 175H made for weight 87-100 kg should be fine for you.
The Dual 168 has a shorter radius and, for you, it should be more a toy for playing around (powder, bumps, carving). While the Extremecarver will give you more if you want to push the limits on the slopes. Of course it is excellent for standard carving too. The Gen5 has an excellent pop for this purpose too (fast carving, small turns), while the Pro2 has an excellent comfort and dampening.
The Swoard team