Hello!
Traveling 3/28/2026 - 4/4/2026 Starting from Frankfurt to Geneva Switzerland. Would like to do a scenic route along the Rhine River (would that be a Regional Train?) but I don’t know if a Eurail Pass covers that.
Eurail pass covers nearly all more or less direct trains between Frankfurt and Geneva, no reservations required. Add a stop on Schloss Laufen am Rheinfallen for the most scenic views of the Rhine waterfalls. Depending on your ambition and how much time you're willing to spend in a train, you can add some other scenic routes as well through Switzerland, though the direct route will be far faster (from Frankfurt towards Basel and from there towards Geneva).
What do I need to know about crossing into Switzerland? Do I need to go through customs?
Switzerland is in the Schengen area (meaning there are no systematic border controls) but not in the EU Customs union. Unless you have something to declare (which you can do at most major train stations in Switzerland) you can simply continue your journey.
Do I need to get any other passes for Germany or Switzerland that would make traveling easier. What about passes for taxis?
I don't think there is such a thing. Your Eurail pass covers trains between cities, my recommendation is to chose accomodation close to a train station (eg in Frankfurt you can use your Eurail pass on the suburban S-bahn trains).