Maybe to clarify:
the GW1100 and the GW1000 are a display-less console, a "gateway"
GW1001, GW1002, GW1003 are stations, i.e. the GW1100/GW1000 console + different sensor/sensor array combinations
I strongly recommend to completely and thoroughly read https://www.wxforum.net/index.php?topic=40730.0
Once you are through, you should be clear.
A GW1004 is not an official station sold at Ecowitt.com - it's however sold as a (I would say cripple-)station at amazon.com and ebay.com as @zoomx says: GW1000+(1-8)WH31.
Maybe the target group are people who are only interested in temperature and humidity (and air pressure).
The GW1100 has a bigger internal memory (to accomodate a WebUI) and therefore a different firmware from the GW1000.
The API by which it communicates data to software applications like CumulusMX is still the same.
It can be managed through both either the WebUI and/or the WSView app