How do you mean 'online transfers'? do you mean bank transfer payment from your account? if you do they why are you even bothering to ask about anonymity because that is the least anonymous method you could ever use. Putting some separation between you and your bitcoin acquisition means buying them anonymously, having no links etc. Buying them via online transfer is one solid link I might add so I would strongly advise against that. If you can pay by cash deposit over the counter do that.