Tewi: This is a potentially big topic we wanted to make a whole guide for in the distant past, but were never successful enough with lucid dreaming to fully explore it. In short, yes it is very much possible to use dream characters as a mental basis for creating a tulpa, and it probably makes the process a little quicker.
As for the question of whether forcing/developing your tulpa in lucid dreams can help in waking life... We assume it could help a little as long as there is still waking interaction and reflection on it as well, but we never got to test it out fully. Consider it supplementary, but not able to fully replace waking forcing. (And we do think "waking reflection on the dreams" is necessary to connect it for tulpa progress) (edited)