Schengen visa wil get you through all schengen countries.
Best combination of both convenience, comfort and value is the train. There is a TGV from Paris to Basel, where you can change for a train to Interlaken. There is also currently a direct Paris - Interlaken TGV, but it arrives at an inconveniently late time, and is actually slower than changing trains in Basel.
If you have Schengen Visa then you no need to issue a separate visa and yes you can reach by bus or train but i will recommend you train..you will get much better view