Kpop tends to pile all sorts of acts into the same pool and that rarely helps with valid comparison.
One such case is when members of active/not disbanded groups, do solo activity. They benefit from the fandom of the group, which extends as support for themselves. It is only when the group has gone inactive for few years, people would know whether the member truly has fans for themselves or just benefitting from the groups.
So I think these individual ventures should be treated similar to SubUnits of 1, i.e. SolUnit.
To differentiate from Soloists whose groups were in the past, or were never in any group.
Jennie, Jisoo, Rose, Lisa, Nayeon, Jihyo, Suga, RM, Jin, Jimin, Jungkook, Jhope, V are all SolUnits at this point. Even Chuu, Jinni their identity is tied to their groups.
Taeyeon, Hyuna, Sunmi, Chungha, Hwasa, Solar, Wheein, Somi, Sejeong, Kyunhyun, Kang Daniel etc., their group days are long gone, so can be considered Soloists.
Even Baekhyun, D.O., Suho, Kai are getting there.
Ailee, Lee Hi, Heize were always solos, but maybe not idols for they never went through the idol trainee process & debut.
Of course the anomalous phenomenon of Kpop is IU - a true Solo & an idol by training.
So GROUPS, SUBUNITS, SOLUNITS & SOLOISTS