Mountain peak or scenic spots on the mountain 

thanking you

Not covered, but discounts are available.

Here’s an overview: Swiss railway companies with discounts | Interrail.eu

E.g. from Luzern, you’d get 50% when going to Rigi Kulm or Pilatus Kulm (the others mentioned do give just 25%).

Just my 2 cents: Best mountain spot to reach with your pass for free is the Bernina Pass (Ospizio Bernina (2.253 m high) / Alp Grüm (2.091m high)). Also recommended: Oberalppass (2.033m high).

For the railway from Zermatt to Gornergrat, there’s no discount with an Eurail pass.  

For included panoramic journeys I’d recommend the Bernina line, no need to take the panoramic coaches there are hourly regional trains on the same tracks. And you can use the Bernina Express in the reservation-free coaches at the front if needed.

As an itinerary : Zermatt - Brig - Andermatt - Disentis/Mustér - Chur (Glacier Express route, there are hourly regional trains without the expensive reservation).

Then from Chur, the Albula line - St. Moritz (you can bypass it) - Bernina line to Tirano (Italy). And then either a bus to Lugano (included but there is a mandatory reservation fee) or back on the Bernina Line - Engadin Valley - Vereina Line - Landquart - Zurich - …

Montreux - Interlaken - Lucerne is quite scenic (boats included on Lake Thun and Lake Brienz).

The Old Gotthard Line is particularly nice too !

Let me know if you have another question.