I don't have many dwarves in my fort. This is not only because it helps my fps, but because that way I can have a closer relationship with a few of them. Dwarves who are of specific interest to me I might ennoble, etc, or give special rooms to.
I go by the colours. I usually know the purple ones quite well: One is the broker, another that damned mayor who keeps mandating things. Red dwarves I might follow around watching them make traps and wells and pumps. I love watching miners mine. I rarely watch green dwarves go hunt, although I often intend to.
Most recently I've been watching this:
See the red mug? That's a pink gemstone artifact mug. It was the first artifact in GuildPlunge, and is a really popular drinking vessel. It moves around a lot, and as I have unbinned mug stockpiles near all the food storage areas, I can always see it somewhere. I will admit, for me, that is one of my main characters in my fort, and a very active character too, that mug.
Here it is downstairs:
Someone walked up 100 flights of stairs, just to get the most favourite mug of the fortress. It's almost always in someones hands, unlike the brass goblet next to it, which is pretty, but not as popular. Later on, the mug was again seen upstairs, abandoned in the middle of the still.
I've not heard of any mods that make dwarves more recognisable, but I think I'm managing to recognise specific characters, even if they aren't dwarves. It's like an ant farm: I might not be absolutely sure who is who, but I can make some guesses from their work.