Geneva airport has a "Swiss side" and a "French side". Cars rented in Switzerland will have a "vignettes", which you must have for motorways. Cars on the French side are sometimes cheaper, but probably won't have a "vignette", so you'll need to buy that and add it to your cost comparison. If you drive a car without a vignette on a motorway, you will very probably be caught and fined.
If you want an automatic, you need to reserve one. Otherwise you'll get manual transmission.
There is no "normal" cost. Pricing is dynamic. You just have to get quotes and see who has the best deal for your dates.