Im trying to keep this simple:

Nit: something like 19/18 and below
Reg: everything between like 20/19 and 30/28
Fish: everything that is weired: so hard to put in concrete numbers, but like high vipip, huge gap between vpip and pfr, high/low 3bet, weired cb stats, ....
Whale: vpip 50+ and mostly low pfr

But im trying to write concrete notes that i can generalize fast, like: „floats too whide“ or „doesnt bluff weak flush draw OTR“
Dont see too much merrit in notes like „played x on y for X/c“

Must Play - Crazy Fish, they do something extraordinary in a hand
Under 100bbs - Going to be generally weaker player
Tight Passive- Good VPIP, Low RFI, Low 3BET
Tight Aggressive- Good VPIP, Good RFI, High 3BET
Loose Passive- High VPIP Low RFI Low 3BET
Loose Aggresive- High VPIP, High RFI, Hight 3BET
Note Label - Just have a note on someone, like snap checked back easy value bet, but no real sample

All TP TA LP LA have over 100 hand sample.

Nit, reg, reg fish( 30/11), fish, whales. Now when I dont have stats I keep it simple: reg, reg fish, fish and I make a lot of notes.

Cool many thanks guys looks I am pretty much on the same labeling system, only diff is the 100hands(will start doing so) and separating regs from tag and lag. Thanks!!

In general I dont think its good idea to make labels only based on preflop stats - you have this in hud, so why make informations on table redundant? Additionally poker is game of limited information - what you know in general stats on small sample can be false when you get more hand on opponent. I label by vpip only nit, and few times I saw that player who was 17/13 after 500 hands went to 28/22 after 2k hands. Thats why I focus mostly on player tendencies I witnessed.

Nit - > for regular that has very tight vpip(<20)
Reg -> for every type of regular, general tag
Aggressive Reg -> exactly as label states
Station Reg -> for regulars I saw calling marginal hands few times
Bad Reg -> I give this when I see COMPLETELY missplayed hands or huge leaks.
Potential Fish -> I give this label for everyone that did something fishy like limping, min3betting or dont have full 100bb stack
Spewer Fish -> for aggressive fishes who bluff a lot
Station Fish -> recreational who calls too much
Whale -> fish that did some ridiculous things and clearly has completely no idea what he is doing.

I play on an anonymous site so I have to do my labeling in real time. I use colors like Blue for Bluffy, Purple/Violet for Passive/Value heavy, Orange for sticky (orange juice is very sticky). That way I can quick glance and I know what they did last time.

I use Green for any short stack = I click them and simply note stack depth i.e. 50 for a guy why is playing a 1/2 stack. I keep them green as I see any dumb stuff, etc.

I use Red if I see aggression with a "value" hand and a Darker Blue if they spewed off a stack preflop (i.e. some guy 4b+ with A9o). I also keep them red if they are very very tight.

I use a lighter blue if I see them bluffing or value betting super thin postflop. If I get donked into and he folds to a raise, I tag him light blue and note "donk/folded xxx board" for example.

I use Purple (Purple = P = Passive or Violet = V = Value). If I see a guy triple off with the nuts, he gets that tag and a note "3 = value".

I use Orange for guys that are sticky, like some dude calling down 3rd pair vs big bets.

I use Yellow reg types.

One thing that I have found that helps me from getting distracted trying to write out notes and keep up with 4+ tables is to continuously create notes in Word or Any Document program and then I can quick copy/paste the standardized note into the box and not get distracted.

Stuff like:

Donk/Folds flops
X/R bluffed flop
ETC.