Hi Shireen
Looking at the definitions of the various macrostructural features in the original paper that defines them (and also the definitions in this table), it seems like the “length of the fiber bundle” is essentially the mean track length of all streamlines in the bundle, which is what you would get from tckstats. I’d be careful here, as you want to be sure that all of the streamlines in your bundle do in fact traverse its entire length, which depending on the seeding / ROI strategy is not necessarily guaranteed. The tckgen options -seed_unidirectional and/or -stop might be useful there. The endings segmentations functionality provided by TractSeg could also be useful there.
As for the other properties like surface area, those are also defined mathematically so with a bit of creativity you should be able to at least approximate the same proceedures in MRtrix. E.g for the surface area, it looks like that metric is based on the number of surface voxels of the bundle segmentation. You could use maskfilter erode -npass 2 and subtract result from the original segmentation to get the “surface” voxels (similar to the process for creating a glass brain), and then count them up using mrstats -ignorezero.
(disclaimer: these suggestions don’t claim to be able to exactly reproduce the methodology of the paper in question 
)
Hope that’s helpful!
Fiona