All the control software in in the 1234. You just access it from a PC and it “serves” up the various windows and menus that you need.
While it can be a challenge to get going, you also have to forward ports in the router at the host location so the 1234 can be connected to from the outside world.
If what I just wrote makes sense, then dive in, but at this point I’d wait for the 1234B using the RPi4.
If none of it makes any sense, then you’re in for a challenge and an education, but it would be good if you had knowledgeable assistance familiar with port forwarding for one and interfacing radios and computers as well.
Then, after you get it all working, be prepared for RFI from the TX causing issues. Good engineering practices and liberal application of ferrite beads of the proper “mix” for HF on every cable is needed.