Starting Rhone route -- confused

Hello! I'm planning to do the Rhone route (flying into Geneva in the morning) and am a bit confused about the starting point. Wondering if someone can answer some (probably simple) questions?

- Coming from Geneva, should I take the train to Obergoms/Oberwald or Realp?

- Where is the actual "start"?

- If I start in Obergoms/Oberwald I don't get to ride the furka pass, right?

- Where's the best place to stay (not camping) the night before starting?

Thank you!