I was too looking for a Japanese keyboard as a new Japanese learner. None of them seem to support it yet.
Fctix has been kind of a blessing to me, since I don't own a PC sadly. I agree the typing kinda sucks, it has less functionality. But as for space after a selected suggestion word you can configure that behavior in the settings.
Anyways I do hope the Japanese keyboard input will be supported on the more optimized keyboards eventually, if you find anything better before I do please let me know!