I always felt that the 'personality types' of the Klingons and Romulans were swapped after the TOS (during one of the first movies), and just the other day I was reading something that said they legitimately were - that in one of those early movies* the baddie was supposed to be the Romulans, who were then swapped-out for the Klingons, but the script was left the same, which then gave the 'honorable' vibe the TOS Romulans had to the Klingons, and the Romulans became the bloodthirsty war-mongers.
Anyhow, I was glad to read that, because all these years I had felt that way and then it was finally confirmed, and there is a very RW reason behind it. I just wish I recall where I read it. LOL
You are making me want to watch that now... NO! I won't do it! {stick fingers in ears and goes "la la la la la.." really loud}
But yeah, thats been my assumption for awhile now, and that time period when the Klingons stopped using Cloaks ("No capes!") was when one of the more 'Conservative' (Kahles-following) Houses was in charge.
*Probably the movie you mentioned - Star Trek III