I built my second astrobox and am using a tontec 7" touchscreen display. It works well but requires the use of an additional 12v power source. I am getting the official raspberry pi 7" touch to test with and it actually used the pi board for its power.
I also found these need jewels for powering the raspberry pi:
I now have my printers setup where all the power comes from the main transformer, My lights to see the bed, and camera’s and now the raspberry pi.
I use these off of the 24 volt power supply to get 12v or what ever I need: