Early JP DOW vs Hongkong and other Asia-Pac territories

[jjdenver]

I recently had an opponent DOW very early (I think spring 41?) on Hong Kong, blockade Australian harbors, and I think he took Sarawak and Brunei. I don't remember everything that he did but has anyone else seen this? Can JP safely (without much/any diplomatic consequence) DOW even Britain? NEI? Basically what are the parameters that JP has to work with when doing this kind of early activity (before USA is in the war)?

Also a very different small question - does Germany suffer diplomatic negative if it DOWs Luxembourg on turn 2 or 3 instead of waiting until the Belgium & Netherlands are attacked?
EDIT: I think for sure GE gets negative consequence diplomatically for Luxembourg. Is there a more clever way to DOW? I tried to DOW Belgium and it seems Luxembourg and Netherlands don't auto-join allies (I thought this might be a way to avoid negative consequence for DOW vs those 2 countries). Maybe leave Luxembourg and Netherlands alone until after USA joins the war? Is that a good way or realistic?

[Coaltar]

I would think the only impact is that mobilization numbers will likely increase for specific potential enemies. Just opinion though.

[Bavre]

On the original topic:
Declaring war on the Dutch will cause Belgium to join the Allies one turn later. So you can save one DoW at the cost of a stiffer defense in Belgium.