Encounter base is about 1000, plot about 12000.
The number of sessions does impact it.
The number of clues doesn’t.
Relics don’t.
Running for the same people doesn’t.
The more you run things the lower the rewards though, so people running plots on cooldown will get less per plot than people doing so more sporadically.
It’s assessed over several categories independentally and then the scores are combined, the categories are stuff like narrative flow, player agency, cohension and believability, story arc resolution, writing quality, interesting moments, and some anti-scores like fluff or padding.