Welcome back! For others reading here, this is a honeymoon trip.
With your interest in nature and scenic beauty, I suggest you focus on that in Switzerland, and not spend 2 nights in Bern. You already have some “city time:’ in Switzerland with Lake Geneva (Lac Leman), and Luzern, and more in Italy.
A few suggestions, mainly for Switzerland:
If your flight lands in Geneva in the afternoon, consider taking the train directly to Montreux and spend 2 nights. Book a nice hotel with a lake view, such as the Grand Hotel Suisse, or another. Spend the day strolling the lakeside promenade, or visit Chateau de Chillon.
Next take the scenic Golden Pass train from Montreux to Interlaken Ost, where you change to the local train to Lauterbrunnen. You have allotted 4 nights to this area and that is good. Lauterbrunnen is a beautiful valley that many compare with Yosemite in the USA. The views from a hotel there will be of the walls of the valley and a waterfall, like this:
https://lauterbrunnen.swiss/en/
For stunning views of the mountains, you might consider staying in one of the alpine villages above the Lauterbrunnen Valley. From Mürren you can see views of the mountains across the valley, like these from Hotel Alpina which is right on the edge of the cliff:
https://www.alpinamuerren.ch/en/hotel
Or you could stay in the village of Wengen across the valley, which has more upscale hotels, and views like these:
https://www.silberhorn.ch/en
https://www.bellevue-wengen.ch/en/home/
Here are the views from the webcam there:
https://bellevue.roundshot.com/#/
After your time in or near Lauterbrunnen, return to Interlaken Ost and continue on the scenic Golden Pass train route to Luzern to spend 1 or 2 nights.
From Luzern, you have 2 good options to reach Lake Como by very scenic trains or boat/train combination.
(1). Take the Gotthard Panorama Express boat plus train, ending at Lugano in the Italian-speaking Ticino region of Switzerland. You can overnight here, or change to a train heading to the town of Como on Lake Como, 35-45 minutes away. Spend 1-2 nights here, then move to Varenna either by taking a boat up the lake, or train to Milan and change there for Varenna (1 hour away by train).
You can watch the video of the Gotthard Panorama Express on this website:
https://www.gotthard-panorama-express.ch/en/
The Gotthard Panorama Express is all First Class. For a less expensive journey with the same scenery (same boat and same train tracks), you can ride the ferry to Flüelen and take a regular train going toward Milan to reach Como. You may have to change trains on the way. Or you can skip the boat and take a Treno Gottardo from Luzern to Bellinzona, changing there for the train that will take you to Como.
OR (2). From Luzern, ride the train to the mountain village of Pontresina, 4.5 hours away. Overnight here, and the following day you board the Bernina Express train, or a regular train on the same tracks, for the most scenic of Switzerland’s named scenic trains. This will take you to Tirano on the Italian border, where you change to an Italian train going straight to Varenna. The entire journey is 3.5-4 hours.
After your time in Varenna, you continue to Milanand/or Como. After that to Milan where you catch a fast train directly to Venezia for your cities in Italy.
