Sorry if my post came across as a rude comment…not intended that way but more to say “don’t worry”, a 30 year old man will decide what “look” is good for him on his own BUT that if you’ve never needed a boot things that are important are sole grip, height of boot, SOCKS! 
Sorry OP!
Socks!!! On really cold weather days, a thin liker sock and a thick outer sock will do magic.
Mr. B swears by his Eccos when he has to travel to colder places. They look like dress shoes whith dress pants over them. Ecco also makes sneaker-like waterproof boots.
My son didn’t wait. He ordered online a boot he liked, in 2 sizes. No he didn’t tell g/f what kind. If he doesn’t like them. Then he’ll go to mall
But we enjoyed reading and getting great suggestions. I’ll encourage the socks