I have had some cockerels that feather in VERY slowly. Then, on the other hand, others that feather in normally. As far as feather quality - your confusing it with Lavender. Lavender has some major issues (fretting), while chocolate has the issue of becoming dull and diluted without the addition of black. For some reason, black brings back the darker, richer chocolate color.
White feathers are normal on black and chocolate chicks. They will fall out and be replaced with normal colored feathers for the bird.