EAM is the best choice since its cloud will be used by OA, EAM uses High RAM during updates and boot only, after it is quite light. If you really dont want EAM, any AV that doesn't incorporate an HIPS is ok.
May i ask what is your system 32 bit or 64 bit, how much ram do you have?
I ask, as i run both Online Armor and Emsisoft Anti Malware, and on my 64bit system with 4 gig of ram, i rarely go over using 35% with everything open and running.
As stated,, the best course is to test a few your self, depending on your specs and uses..
Last time I used Avast with OAP which was sometime last year, I ran into problems as I kept getting BSODs which was a known problem after I looked it up, I don't know if its been fixed.
I wouldn't try Eset with it as I used it recently and my system kept freezing up.