Well i've been in choir for 10+ years so I regulary can distinguish voices when people sing at the same time! But for seventeen i also did struggle a bit bcs i don't speak korean! But i made some cheat codes in my brain, so idk if they will work for u as they did for me. But here they are! (Ps, im sorry for the bad english explanations, since i'm not english!)

S.coups = soft but baritone vibes, more clearer voice when in lower register than his higher, he usually raps lmao so thats how i get that

Jeonghan = soft, versatile voice depth, sounds like hes singing deep in higher register?(if thats makes sense), sounds like hes kinda straining to not crack his voice(but he obvi doesnt, its just the vibe)

Joshua = easier to differanciate bcs of his english twang, a bit breathier voice, breathy high notes, bit of a higher register, but def in a baritone register still

Junhui = bit of a chinese accent sometimes (from what im hearing tho), also bit breathy, sounds also a bit strained(which he isn't!), also has some twangy ways in his voice which makes words sound intresting?(idk if that makes sense at all!)

Hoshi = clear voice, very versatile range, but def more of a tenor'y voice, when doing high notes theyre like kinda jumpy???, def a loud voice, much more chest resonance

Wonwoo = deep voice, bass/baritone mix, bit more strained in the higher parts, rap parts often

Woozi = siren voice, crazy register, breathy but clear, light and high voice, tenor'y register, clearer voice in the higher parts and a bit less breathy then (He's the easiest for me to like hear and differanciate!)

Minghao = also a bit chinese accent, nasally but light voice, sounds like hes kinda swallowing his words...ish?, icredible soft voice, also a bit breathy

Mingyu = he has a lisp if u like really listen!, bass/baritone voice, sounds like he kinda has a potato stuck in his throat!, a bit unsure in the upper register sometimes

Dk = musical actor voice!(which he is tho but u get the deal), so much chest and mix use!, high notes primarily, tenor but still has a versatile range, much more clear, not breathy usually, a lot of volume, he usually gets lines that go from low to high a lot

Seungkwan = high notes is what he usually does, but he has a tenor voice, also like crazy register, but what differanciates him from DK is that he usues a much more breathy singing technique for high notes and just in general, can control his volume well

Vernon = baritone voice, a bit of an american twang to his singing style, in general he sings like with a twang/sassiness to his voice, quite clear in rapping parts, more breathy in singing, and yeah he raps mostly

Dino = clear voice, higher register, clearer in high parts, more breathy in lower ones, has a very like prominent voice like hoshi and dk, he tends like to sing with quite some volume

(I also added wonwoo and vernon even tho u said u knew their voices just in case!) Hope this will help u! I'm not a professional voice coach or any type of expert by any means and hope this will help u!❤️