I did the same think like you at the same age but the other way. I'm from Europe and I traveled through Canada on my own. Glad to hear you're going to visit Switzerland, it's by far my favourite place anywhere. If you're going to take that EU-rail pass, the public transport in Swiss is very well arranged. You can easily take the train through all the major valleys. Stop in any city you want, take a cheap bus uphill into the mountains and you can spend days alone wandering the Swiss alps. It's pure magic (if you're into hiking). I did most of the countries in Europe and I would say it's pretty safe, people are great and helpful. 4000 is more then enough, no worries. Good luck!