Yea each one runs through the previous module, so all the power goes through the first module.
IEC 13/14 connectors are rated for 10A (2300 W at 230 V) which isn't much lower than what you can run through your wall outlet. And in reality they can probably handle 15A(What your wall can handle) as they are commonly refereed to as "Kettle cords" and used by kettles which draw ~13 Amps.
That's very high, to give you an idea the 6 things I have plugged in draws ~240w, so I could chain up ~60 mini PC's and only then would I be over the ~2300w limit.
I do now mention this in the Safety section of my "How to build this" write up


