Is it realistic to mix passenger and goods wagons on the same train?

Yes, it is realistic to mix passenger and goods wagons on the same train in certain situations, both in real life and on model railways. Historically, it was not uncommon for passenger trains to include a few goods wagons at the end of the train, particularly on branch lines or in rural areas where there may not have been enough freight to warrant a dedicated goods train. This was especially common in the early days of railways when the volume of freight traffic was relatively low.

In terms of modelling, including a few goods wagons at the end of a passenger train can add an interesting visual element to a layout and make it look more realistic. For example, a model railway enthusiast modelling a small rural branch line may want to include a mixed train that carries both passengers and goods, just as they would have in real life.

However, it's worth noting that mixing passenger and goods traffic on the same train is not always prototypically accurate. In many cases, passenger and goods traffic would have been kept separate on dedicated trains, especially on mainline routes with higher volumes of traffic. Additionally, there are certain safety regulations and operational considerations that come into play when running mixed trains in real life.

Ultimately, whether or not to mix passenger and goods wagons on a model train will depend on the individual's preferences and goals for their layout. Those seeking a high degree of realism may opt to keep passenger and goods traffic separate, while those more interested in creating an interesting and visually appealing layout may choose to mix them.