For online information, try the Swissgeo website. You can zoom in to an incredible level of detail. You can save money by only buying more general maps of many areas of the country (I have the set of about ten 1:100,000 composite maps from SwissTopo that covers the whole country), then before you go to do a hike, look at it closely on the Swissgeo website, and mark on or write down separately any trails or features that are not on the 1:100,000 map. It's worked very well for me so far. Only for my local area do I have a more detailed map, 1:50,000, because I use that more often. The trails are sign-posted so well and are so easy to follow that I haven't needed any more than this so far, and I've done a fair bit of hiking.