visa needed for the flight Melbourne - Shenzhen (SZX) - Beijing (PEK) to Amsterdam ?

Hello, I have booked an one way flight with China Southern Airline from Melbourne/Australia to Amsterdam/Netherland via Shenzhen (stop ca 2h) and Beijing (ca 4h)
I am an German passport holder, my wife has an Indonesian passport and german permanent stay permission card
Will we need an China transit visum in advance or do we get an VOA?
Will the situation change if we fly via Guangzhou - Beijing and not Shenzhen - Beijing
(I read Shenzhen airport has a special visa policy)
Thanks a lot for your help
rgds Frank