The qualifying gaps are the same, no matter what is a qualifying time delta, no matter what form of racing.
In GT7 the gap between cars is annormally large, I believe due to flawed graphic processing, as the frame rate drops are noticeable when you have multiple cars on the screen. I think PD put intentionally the grid well spread to minimize the number of cars to show in almost full detail.
Not a rule on mainstream racing.
F1 and subsequent FIA series, after the leader passed the first safety car line, which is well before the start finish line, the racing starts (in case of slippery surface, race director can decide by a rolling start) or is resumed and everyone can pass even before the safety car line.
In NASCAR, there is the GEICO Restart Zone, which is marked on the exterior wall, usually midway between last corner and start/finish line, were the race starts or is resumed after every caution.
Neither case the start/finish line matters.