Re: the description of British Army officers, I think that definitely agrees with Keith's thoughts here: That model young man—he could not be more than five- or six-and-twenty—reading the Church service every Sunday to his household! He thought of the young men of his acquaintance in the army or in the fashionable world of London, the careless, loose-living subalterns, the young beaux of White’s. Ye gods, what ribald laughter would have gone up at the tale!... Yes, but not one of those potential mockers could have beaten Ardroy in stature or looks or at swordplay.

And yes, good point about Ferrers ("elegant" and "exquisite"). To me it's pretty much impossible to read Keith as straight, but I do see him as being attracted to women as well. Here are his thoughts about Alison: Who was this pretty Miss Grant with the blue fillet in her dark hair—a kinswoman? If she was the future mistress of the house, young Cameron had good taste. So, to be just, had the lady. Heh. Then there's Lydia, whom he apparently cared about enough to be hurt at her betrayal.