FWIW, on my old 1.5GB Atom powered netbook I used to use either K-Meleon or the XP version of PaleMoon (archive link) which had optimisations for Atom CPUs.

FWIW played with K-Meleon for a couple of days and it was terrible.  For the moment I'm assuming its the browser and not some other issue but I'll give palemoon a go and see what happens

Could be a rebuild in the works...