With a mech use known batteries, Efest is known for inflated specs, so don't use them. for 18350 indeed go for AW, for 18650 go for Samsung, Sony or LG....and get them from a reliable source.
I had a Atto from 3fvape and it was a pretty nice device, but mechs just aren't for me, so I sold it a while ago.
Be sure the 510 pin stick a bit out below the threading, as the Atto is a semi-hybrid, also take a good look at the battery orientation, as it is the opposite of what most mods use , there should be a picture on the mod in regard to battery placement.
And I think I remember it only takes button top batteries, but not sure anymore, so take a look at that too.