Learn English – Technical term for associating a group with the actions of a few

You might be able to use the term "East Asians". Of course, you have to consider whether your audience is sufficiently familiar with the East Asia region or not. Also, Mongolia is at times included as an East Asian country; and to further muddle the boundaries, some people use the term "East Asia" to also include Southeast Asia (not a practice I personally approve of).

In order to avoid any ambiguity you could define the term when you first use it in an article, e.g. East Asians (i.e. people from China, Japan, and the Koreas).

As for "Oriental", I don't believe it carries a negative connotation in most of Europe (but I'm not 100% sure on this). To me, the term carries connotations of romanticism and adventure - probably because of the Orient Express. However, it is definitely an antiquated term and on that basis alone I would recommend you not to use it. The fact that some people (possibly a large amount of people) take offence to the term is another good reason to phrase it differently. Note that both Oxford Dictionaries Online and Merriam-Webster list "Oriental" as having negative connotations. (Also note that they disagree somewhat on the geographical scope of the term, with the former dictionary interpreting it as referring in particular to East Asians and the latter as referring to Asians in general.)

And what do you mean by people from "this part of the world"? Are you referring to actual Chinese, Japanese and Korean citizens or to people who can be ethnically classified as such but are citizens of countries outside of East Asia? I can tell you that my Chinese friends (Chinese nationals) aren't even familiar with the term "oriental" and that they would refer to themselves as Chinese (and that makes perfect sense as you would most likely also refer to yourself as American rather than North American if someone asked). If they'd use a regional term they would definitely go with "Asian" - but as you already noted, this term is too broad to be of much use in many cases.

1. For the first artistic display, I would suggest mass choreography. A mass is a name for a large group of people while choreography means a sequence of steps and movements in a staged dance performance. If you Google mass choreography there's a choreographer called Penny Jones who seems to specialize in this form of dance composition. Watch the Arbank, a Turkish bank company, TV commercial.

It's by pure fluke, I discovered who the choreographer is for this TV advert.

There is another dance term called tableau which means a pause during or at the end of a scene on stage when all the performers briefly freeze in position. The website about.com says

A ballet choreographer sometimes creates a striking tableau by arranging the dancers on stage in a unique formation. The dancers strike their individual poses and remain motionless and silent until the curtain is closed.

One renowned American musical choreographer during the 1930s was Busby Berkeley

Berkeley devised elaborate musical production numbers that often involved complex geometric patterns. Berkeley's works used large numbers of showgirls and props as fantasy elements in kaleidoscopic on-screen performances.

As a choreographer, Berkeley was less concerned with the terpsichorean skill of his chorus girls as he was with their ability to form themselves into attractive geometric patterns.

2. The term silhouette means a representation of someone or something showing the shape and outline only, typically colored in solid black.

The expression silhouette performance seems to encapsulate the art form presented by the BGT entertainers Attraction.