Can you please tell me what is the make and model of the all in one machine you have? I want to find out what GPU you have in the PC.
MST (Multi Stream Transport) can drive each display independent and SST (Single Stream Transport) runs spanning as you describe.
In Radeon based GPUs you can run in MST and you can form a SLS panel across 3 or more displays, AMD named this feature as Eyefinity as an example.
Please get back to me on the question above and I will see if your GPU is supported.