Taeyeon and male idols lol, since her Chinchin days she always seemed more comfortable with guys than girls being able to "bro down" with them but nowadays girl can't use the same snapchat filter as a dude without getting shipped and called a slut over it. Heck people even ship her with Heechul and Jonghyun now who used to be two of few safe zones.
Her and Baekhyun are likely still friends (if not still dating) and for instance her and Leeteuk are likely still fairly close (he filmed her goofing off and she uploaded the clip on her IG) but ofc they used to have dating rumours so they can't interact. And technically not idols but I think she's close to the whole AOMG gang and friends too, obviously Tiffany and Gray have already confirmed they're (at least) very good friends, but for Taeyeon you had Jay Park comment on her IG live and Taeyeons comments on Crushs' IG live basically went (paraphrased):
Taeyeon: Hi
Taeyeon: Hyoseob-ah say hello
Taeyeon: Why is your voice like that, is it snot?
Taeyeon: Your phlegm sounds hot
Taeyeon: Are you ignoring me
Taeyeon: Bite him, [name of crush dog]
Jay Park: Hi bro, love you
Crush: Love you too Jaebum
Taeyeon: angry emojis
Crush: kekekeke hi Taengoo