Solved

Which fuel/lap indicator is more accurate?

When looking at team history, just remember that your car/driver have to be near the same in order to get best predictions.

The practice laps are more accurate but often slightly lower than a lap in the race at similar average push level, probably because in the race the laps tend to be faster, which poses a certain risk of underfueling.

The strategy tab, after doing practice laps, is usually off by a larger margin and it usually overfuels. It seems it adds a certain amount of fuel to give a good chance the fuel lasts for the intended stints even if a manager is not live managing and the circumstances like weather change.