Help with Train Route Please!

From Innsbruck, the easiest option would be too take the train to Zürich and continue to Luzern for a few days (I'd say 2-3 nights), then on to the Interlaken area - preferably to one of the villages in the mountains such as Wengen, Mürren or Grindelwald. The Luzern-Interlaken railway is scenic.

Personally, I don't think that December is the best time for long scenic train trips like Bernina and Glacier expresses, because of the higher risk of poor weather, and 7 days go by quickly.

Still, if Bernina is a must, you could easily replace the Interlaken area with the Engadin, which is also relatively easy to access from Innsbruck. Either you take a shortcut by bus from Landeck-Zams to Scuol-Tarasp, or you go around by train via Sargans and Chur.

Füssen is way off the main train routes so not practical in your case.

you may not know that for the big name trains like the Bernina Express and Glacier Express, while the fancy tourist named-trains can indeed sell out, the route can never sell out because there are non-fancy, non-named, non reserved local trains plying both those routes, in fact all Swiss routes, at least every hour. They are cheaper and you still see all the same scenery - they use the same tracks and call at all the same stations (more in fact, so your choice is better) - and they travel at the same speed as the named trains. The have to because most of the lines are single track and the trains are timed so that they pass at stations with two platforms and two tracks - no standoffs.

Have you considered the regular trains or is being on a named train a big part of the experience for you?

Thank you both! I do not need any special train so if there are un named ones I’m happy for it. All we care is for a scenic train ride (in late December/early January).
Where should I look for those no name train routes?
I feel I should have this planned and purchased before I get there, no?

use the operator of most Swiss trains, SBB. SBB is the abbreviation of the Swiss Federal Railways in German. You can also see CFF (French language) or FFS (Italian), but SBB is the most used.

The website is https://www.sbb.ch/en ... be advised that at this minute they are having a technical problem selling tickets online and via their app, that should pass soon.

Just put in your start point and finish point, date and time of travel and you will be given choices. Be advised that the prices you initially see are half of full price - they assume that you, like the vast proportion of Swiss folks, have a half-price card. You can turn that off. So perhaps look for Innsbruck to Pontresina, or any other location in Switzerland or adjoining countries.

It sounds like you're new at trains, you need the help of the Man in Seat 61

Where should I look for those no name train routes?

This map might help you to do what Nigel is suggesting. Find a start and end point and look up the schedule on the SBB website.

https://www.swiss-pass.ch/wp-content/uploads/pdf/swiss-travel-system-map.pdf

Here are some examples of what I like to do as a day trip from my home in Thun:

Luzern - Interlaken Express: I choose Thun - via Interlaken Ost - Luzern so that this slower panorama route will be shown on SBB. After spending time in Luzern I will either return the same way, or take the faster route that goes through Bern.

Golden Pass Panoramic: On SBB I choose Thun - via Gstaad - Montreux. Then same as above, after spending time there I go home the same way or choose the faster route. Sometimes I get off just before Gstaad (in Schönreid) and walk down to Gstaad - an easy walk and very scenic.

You could do this with other starting points and scenic routes as you wish.

I feel I should have this planned and purchased before I get there, no?

It is good to have a plan, but no need to purchase until the day of travel.