The primary difference between a Chromebook and a Googlebook appears to be the ability to run LLM's locally.
The requirements were spelt out at Google I/O. They boil down to a 40 TOPS NPU and a minimum of 16GB of memory. They appear to be trying to match Apple's M series memory bandwidth using software compression. ChromeOS didn't need an NPU and specified a minimum of 4GB of memory. Aluminium OS looks to have the same relationship with its LLM as a Chromebook did with Google Chrome, and needs the hardware to power it.
If they pull it off you will get GPT-4 performance, running locally.
As for who this is for: your guess is as good as mine. But if their replacement for crostini works (crostini is so hopelessly unreliable it felt like it never got out of beta, so it's a big if), even the minimum specs would be a very good Linux laptop.