ALL THREE OF THOSE are, generally, from around 1700 and represent belted plaids in the "semi-formal" kilt wear of the time.
The first 2 were commissioned by Chief Grant and are his piper and champion (which also served as the model for MANY early depictions of Rob Roy). AND, for the LIFE of me, it LOOKS like they have a binding around the ENTIRE perimeter of the belted plaid (look at the bottom and top edges, as well as where the material SHOULD have the cut edge hem).
Interesting.

The third is of a disputed person, of various identifications and, accordingly, the time of the painting. The "Lord Mungo" attribution is the most common one. The latest period one (I've heard) is of a famous actor playing Rob Roy in a play made between the Jacobite rebellions (and sometimes dated to Walter Scott's period, a century later). If Matt says it is Mungo, I put weight on his opinion on the matter. Of NOTE is that HIS kilt has a RATHER DIFFERENT bottom edge than the tartan itself, MUCH more "black" with brighter line right near the edge.