I have had the opportunity to visit a couple of factories whilst I have been here so can answer some of your question!

Jigs - A lot but they are probably not as complex as you may expect (The reason that some brands get poor reviews) - they consist largely of a flat bench , basic positioning blocks a drawing and some fast setting glue (Hot glu or CA in many cases).

the lines that I have seen range from
10 - 20 people building Fuses, 10 - 20 people building Wings, 5 or 6 people building tail feathers & 10 - 20 people covering.

to

1 person Operating the Laser Cutter to feed all of the people and for each model there is 1 person building all components, 1 person covering & Finishing and one person painting - that particular factory specialises in F3a and 3d models and only builds around 5 of each model per month (about 8 models in their range) and they are as good as any Kit I've ever seen built. In the meantime they keep the laser cutter and packaging people busy making "Foamies" for another company.

In all cases there is a lot of additional people packaging etc and keeping the machinery busy on other projects. All of the factory owners seem to fly a lot - and quite well. It's also interesting to see many components being made for some of the traditional "Non Chinese" brands!!

The quality ranges from incredibly good to quite poor - but this is largely dictated by the customers by what they accept and how much they will pay. The people here will produce exactly what you ask for - you just have to ask.