I've always liked how how FASA did it.
My continuity is by TOS movies/TNG/Ds9/SCE, I make the Klingons into the Romulans, The Cardassians into the Klingons and the Romulans into Tholians.
I wish this was the way it had been handled. It would have been better.
However, The TNG Klingons and Cardassians were two of the few things that TNG excelled at.
Of course, Bad Robot wise, I've given the Klingons helmets, cloaking devices and heck, I've even given them back their batleths.
In the end, it's makeup.
What about some photoshop to help in this discussion?