I don’t know how much time you have or how far you are willing to drive, but …
The drive between Reno, NV and Sacramento, CA is absolutely beautiful, and I-80 follows the tracks much of the way, or sufficiently closure to make the drive worthwhile train watching-wise. If you obtain a good map that shows the tracks, your trip will be even more enjoyable. The line is the route of the old “City of San Francisco” passenger train.
You could return through the Feather River Canyon via Portola, CA, the rail line through which is spectacular for miles and miles and miles, with the road following the rail line much of the way. The line is the route of the old WP-D&RGW-CB&Q “California Zephyr.”
You might make a complete circle in a day, but two days are needed to do such a visit justice.
As far as the Tahoe area, Union Pacific does NOT run a whole lot of trains, neither through the Portola route. But, the rail scenery is just super!
Enjoy your trip whether you drive the circle, checkout the immediate area, or just park and breathe in the fresh air!
Donner Pass is NOT a high volume area. So, much waiting is often necessary. Waiting and waiting.
In today’s environment where suspicion runs rampant, it may be more advisable TO KEEP MOVING and look like everyone else in life.
Donner Pass is also a Union Pacific rail pass now, and UP crews and workers are notoriously paranoid. Railfans adapting to this unfortunate situation may be the course of wisdom …