Sounds like it's going to be a great build.

Streamers - unfortunately, there's no specific information on these ID streamers, only anecdotal information. Like you, I've seen all different sizes. Logically, they have to be seen, so I imagine they would tend to be lengthy, but not so much that they might interfere with ops if they drooped.

Interestingly, Maru Special #99, which is more of a war history volume, has a painting of Chokai at Savo on the cover flying streamers. However, these are more like windsocks. See the middele image on this Ebay link: https://www.ebay.com/itm/404385198285

Either interpretation could be ok; there's nothing to contradict either of them.

Yes to white topped directors at this time.