hair is part of our appearance and kibbe does give hair recommendations for each type id. however, kibbe enthusiasts disagree on the level of importance that should be placed on hairstyle.
*I'll mention male and female examples, although, most of the discourse is factored more with (stereotypically) women's hairstyles. but it's all pretty much the same. long/short hair.
for Rs and TRs, short, soft, curled hairstyles are recommended, although longer hair that goes past the shoulders is also good if it retains a curly shape. short types are generally told to have short hair because long hair can look bogged down/too heavy.
MY VERDICT: R fam definitely benefits from hair that has, at the very least, been lifted with a bit of wave or curl! but I'd say hair length is pretty irrelevant, Rs and TRs can look good with hair that goes past the shoulders (maybe not waist length?) [jiwon/fromis_9, kun/wayv]
gamines are explicitly recommended short hair, no longer than shoulders length. gamine recs are made for hair that is short or at least out of the way, for example, high necklines and small details. gamine 'essence' is also chic, modern, and slightly androgynous. kibbe does allow longer hair that is funky, loud and/or shaped in an interesting way.
MY VERDICT: not everyone likes short hair. very few gamine female idols wear short hair on the regular. long hair can be styled (Ariana grande is good at keeping her hair out of her face to fit her gamine outfits) and I find that 'quirky' hairstyles like Seulgi's choppy bangs from 2018 create the same gamine vibe that short hair has. [nayeon/twice, eric/the boyz]
classics don't have hardline recommendations aside from hairstyles that look balanced and moderate. they can be any length, but are usually middle-parted, with a slight curl.
MY VERDICT: really, with k-pop hair styling, I don't think classics have much to worry about. outside of crazy hair (think vintage 2ne1) I pretty much never see hair that looks disharmonious on them. [miyeon/idle, sungchan/riize]
natural hair, like clothing recs, is encouraged to be tousled, fresh, and layered. flamboyant naturals are recommended long, thick, lion's mane like hair.
MY VERDICT: naturals can rock a lot of styles, especially naturals that look moderate. even short/straight hair looks good on a lot of naturals, like Jeongyeon from TWICE. although a lot of soft naturals in particular just get that extra 'oomph' from wavy hair as opposed to having having pin-straight hair. [ningning/aespa, Bangchan/stray kids]
dramatic family recs are divergent between pure Ds and SDs. pure dramatics are recommended to have straight or geometrically-arranged hair, any length, while soft dramatics are recommended to have hair that is shaped, 'big' and glamorous, like a blowout style.
MY VERDICT: k-pop idols pretty unanimously have straight hair that is suitable for dramatic recs and with styling, can achieve a similar style to soft dramatic recs. [yeji/ITZY, zuho/sf9]
To show a broader scope, I have some examples! Long and short hair, male and female.
Top to bottom for families they are:
[Kun/NCT (pure R), Taemin/SHINee (TR)... Gain/Brown eyed girls (R), Eunha/VIVIZ (TR)]
Gamines: [Xiumin/EXO (FG), Felix/Stray kids (SG)... Choa/AOA (SG), Jennie/Blackpink (FG)]
Classics: [Eric Nam (SC), Seonghwa/Ateez (pure C)... Miya/GWSN (DC), Minju/former IZ*ONE (SC)]
Naturals: [JB/Got7 (SN), Junji/Onlyoneof (SN)... Jeongyeon/TWICE (FN), Jihyo/TWICE (SN)]
Dramatics: [Zuho/SF9, Changmin/TVXQ... Bae/NMIXX, Nana/After School]
Soft Dramatics: [Chanyeol/EXO, Rowoon/SF9... Yoona/SNSD, Tzuyu/TWICE]
^-^ that is all for now, thanks!