You will be better to keep yr choice selections within to either the CK100PRO or FitEar F111. I do not recommend picking up the Westone 4's or SM3 v2 for the artist you listen, you will regret it trust me as I'm an avid J-pop lover like you as shared with you during our past conversations last yr, and since over here in Singapore we get chances to audition IEMs easily, I have tried these 2 IEMs out before and they do not fit my taste well for many artistes, especially those J-rock bands you have listed on your first post.
Westone 4 = inherent flaws with the midrange in that presentation is not upfront enough, highs is better than UM3x but is an overall boring IEM for female vocals to me. Is considered a well-balanced and technical IEM to me, but musicality wise falls short when compared to even the UM3x and obviously ranks way lower than CK100/CK100PRO to me for female vocalist.
Earsonics SM3 v2 = Good liquid/lushed midrange presentation. Not recessed as well so it's pretty good for listening to female vocalists. BUT has very very serious inherent flaws with lower-mids in that it sounds too dense, and highs are roll-off compared to Westone 4 or even the CK100/CK100PRO. Clarity/transparency is not something I would relate to the SM3 v2, if you want to feel/enjoy the energy of those J-rock band tunes in your japanese music especially those cymbals/electric guitar, you better not pick this IEM as this IEM is weak when it comes to rock/metal genres as mentioned by someone else already.
My 2 cents.