I can confirm what Chris has advised about Virtual Stopwatch, it will generate lap times in exactly the same way as previous years; i.e. aero efficiency will make a difference.
Efficiency certainly is taken into account for every round. The first 3 rounds are all at tracks which reward high downforce, so for these rounds the main priority is maximum downforce, but for a given downforce level the more efficient car will still produce a faster laptime.
Regarding this question:-
Thus Monaco is not actually Monaco but a variation of the actual track, and so on ?
The track data/layout is EXACTLY the same as last year.. however, since the engine power, vehicle mass, track width, wheelbase, tyres, etc etc are different then the charts from last year will not be appropriate... I guess we will see after the first round how the lack of charts works in practice and we may need to think again about whether we provide them or not. Certainly judging from last years race at Monaco we saw that the car with the highest downforce was the quickest car at Monaco....