Tom is, as always, right on the money.
This helpline has plenty of travel experts who can help you find definitive answers, including the cheapest and most convenient way to travel by train.
What you need in reservations depends on how many, where and when, and what level of comfort, you travel.
Would you fill us in a little of the detail please?
Be careful using the SBB website for prices. It will assume that you have a discount card and show prices at half what you will pay if you don't set the options right.
There are a few instances where a railpass is a good idea, but mostly they are more expensive and especially so when reservations are added on top, along with all the restrictions on passholders being able to get reservations.
Please give us the information to be able to help...