Sounds like a "701 4G".

Its CPU is actually not that much slower than the N270 in later models. [1]
The problem is, that Asus underclocked these Celerons (to 500 or 600MHz) via BIOS settings to increase battery life. Back then, there was a quite popular tool called eee-control, which allowed to even overclock the CPU slightly (I believe the maximum was like 1.1GHz). I'm not sure If you can still find that tool anywhere, and if you would, I doubt it would work with current kernels. But then again, I'd almost expect current kernels to be able to set at least the original clock rate of the CPU without any tools.

The RAM can be increased up to 2GB (single module SO-DIMM DDR2).

There were also some after-market SSDs available to increase the internal storage. But these were comparatively expensive back then and since there was virtually no market for this form factor outside the netbooks niche, I wouldn't be surprised if you'd find any of these left. One also had to be very careful with chosing the right type of SSD, because due to the many netbook models with slightly different specs an SSD designed for one netbook model usually didn't work in another modell (interface type, jumper settings, etc.).
Most people simply resorted to increasing the storage with SD cards. The internal SSDs were hardly faster than good SD cards anyway.


[1] https://www.cpubenchmark.net/compare...&cmp%5B%5D=614