Crouching Height varies based on the characters height and hitbox data, some character hitxboxes remain high despite crouching which in turn may make them more susceptible to things like Instant Overheads and Cross-ups, while some character hitboxes tend to get smaller when they crouch making it easier for them dodge high hitting attacks and even projectiles, the differences are listed below.
Lowest - Chin, Choi, Bao
Low - K’, Andy, Joe, Benimaru, Iori, Mature, Vice, Leona, Athena, Kensou, Mai, Yuri, Yashiro, Chris (slightly taller than the rest), Yamazaki, Billy, Kim, Kula, Foxy, Jhun, Hinako, Angel
Middle - Whip, Terry, Kyo, KUSANAGI, Ralf, Clark, Vanessa, Seth, Ramon, Ryo, Robert, Takuma, May Lee, Shermie, B. Mary, (K9999), Nameless, Lin, Shingo, Heidern, King, Kasumi, Kyo-1, Kyo-2, Xiangfei (slightly shorter than the rest)