Trains is Switzerland are notoriously punctual and though this punctuality is a sense of pride and even joy for the Swiss, it always manages to expose the lethargy in those of us on the opposite side of punctuality.
Renting a car is a good option across Switzerland and may even end up saving you money however you would be devoid of experiencing the best railway in the world, the SBB!
You can buy tickets on the SBB site/app or through GoEuro or at the train station. Also, you can get the Swiss Travel Pass which is not just a train pass but it also gives free/discounted access to numerous other attractions and modes of transport. We chose the half rate card which was perfect for moderate travel that we do, however depending on the intensity of your travel and the duration of your stay you can choose one of the many travel passes listed on the SBB website. If you are younger than 26years of age, lucky you! (check the SBB website for details)
These passes though expensive save you a lot of money if you even intend to travel moderately or visit attractions in Switzerland, half rate pass is therefore a bare essential and it is even valid on most of the mountain trains or the scenic golden pass routes. We got our half rate card from @klooktravel who delivered the physical passes to us in 2 weeks with additional goodies and some discount. Although we had minor problems the klook team helped resolve the issues fastidiously.
The trains itself are largely empty on most routes and you usually would not need to reserve seats also there is ample space to store your luggage in the train or even the train stations (lockers at hourly rates)
Our experience of the Swiss rail system was never disappointing and was enhanced by the experiences we had meeting some strangers on our journey.