This is the best picture of the rear end of the element, and from what I can tell it looks rim brake only
Is there much difference at all in the frames as a couple of disk/disk flows have come up for sale for not a lot more and a fair bit closer
Jitsie are good but I've not tried the 135 stuff yet. The only down side I found with the Jitsie was the drag, Initially it felt obvious but you get used to it only noticable when just rolling around. The tech nowadays is nuts, I'm sure you can hardly go wrong.