Just to answer some of your questions:
Availability is probably in 3-4 weeks (1 week to UK for moulding, 1 week mould-making and casting, 10 days back to Germany).
So once they are ready I will let you know that you can spend your hard-earned cash

As stated the adults are 28mm - a bit smaller than the current Copplestone 30s. The children are between 15 and 20 mm. I have no idea how tall Artizan or Pulp miniatures are as I haven't got any of them but...
Chinese often are a bit smaller than non-Asiatic people so they should fit in with any miniature collection in 28 - 30mm.
The three little buggers form the famous "pigtail parade". It's directly modelled after a contemporary photo done by a German in San Francisco between 1895 and 1910. So there are more to come as it is a real treasure trove for models like these.
The pigtail parade was quite common as the little ones could roam freely in Chinatown but in order not to get lost they held each other at their pigtails. Normally they would be spaced out more but I doubt people would buy 3 different children you could put together.
Something you can't see on the scans:
The little girl's basket is filled with lobsters. And the guy with the two baskets is a "chicken man" so there are a few chicken heads popping out of the baskets.
Hope this helps a bit to enlighten you more
Cheers
JO