I don't understand the different ohms yet...
Its the resistances. For you using an Ego, the lower the resistance the warmer the
vape is. Usually the ohms can be up to +/- 2 of what they say they are. So a 2.0 ohm could be a little lower or a little higher, or it could be 2.0 ohms.
Some people like 1.8 ohms with an Ego. I think starting off 2.0 would give you a good
vape with an atomizer. Higher than, like 2.5 ohms, would work, but you may find it a bit cooler.
A lot of people like the lower 1.8 or 2.0 ohms with Egos.