Hi,
The differences between Etops and non Etops, are based in maintenance procedures and Mel/MMel requirements, i.e. an aircraft to be approved Etops operation need three independents sources of electral power, the 767 has four, two engines driven generators, APU and HDG, you could be dispatched with the APU u/s, only if the HDG is ok.
Another particularity of this kind of operation, is the procedure that involves the engines checks, as oil measurement, two mechanicals are needed to perform this, one for each engine, because this assure to reduce the possibility to duplicate mistakes.
Prior to each Etops flight, maintenance must has been made an entry in the book stated "etops approved" only with this condition you will be able to start a flight extended range operation.
Also, the crew members need to hold Etops Qualification, that involves special procedures like drift down, critical scenarios, etc.
Yours faithfully,