> At least in Japanese, the sound of the character is typed out using english letters

Technically speaking, Japanese have kana-based keyboard layout, where a single mora is a single keypress rather than two. However, there is still an extra (second) keystroke for dakuten/handakuten (か -> が), which is not required with romaji input (where it's just "ka" vs "ga"), so it's not a 100% speed increase. So, typing is somewhat more efficient than with romaji, but I think I've heard no one uses that, except for, possibly, professional typists.