[Silver Fox Phil]

Quite often Hereward, it depends on the standard and quality of the loco. Some are made for Railroad and have less fine detail than say a collectors model. It makes a difference if it's DCC ready or DCC fitted. Some have digital on board with sound, some don't? Lots of variants offer different prices.
I am not a modeler however I do have mounted in cases, some very fine examples of the high quality end of the market, all able to run but no track to run them on(yet) there are some very good molders on here and hopefully they too will add more to your question.
All the best
Phil