Getting to Rhone vallay

Hi all

Anyone have any advice about best (non-car) way to get to the Rhone Alps from Geneva airport. I’m looking to stay in St Jean de Maurienne, near the foot of the Croix de Fer – train looks simple enough, with a change in Chambery, and apparently taking a bike bag as luggage is ok. I’ve had experience of French train conductors before though, who look at you like you’re putting a bomb on their train if its anything other than a suitcase. Anyone got any experience? I’m sort of tempted to build the bike up at the airport, leave the bag with left luggage and ride down, but that would take a bit longer than the 3hr train ride….thanks!