Model railroad approach is different strokes for different folks, some people prefer to just watch. Back before computers SOP to control more than two trains on the same layout was to wire one powerpack to one side of a single pole double throw toggle switch, the other powerpack to the other side, with the common lead going to the track. The track was divided into isolated sections with insulated gaps in the rail, and throwing the toggle switches left or right changed which powerpack was feeding that section. Two trains controlled by two different guys following each other around an oval, or even moving in opposite directions, was possible but took a lot of coordinated switch flipping to avoid loss of control and short circuits.
Computer age changed all that, in 1983 my Dad bought a Keller Onboard kit, which had a constant 14 volts DC on the track with an AC signal controlled by keypads with 20 different channels. A 1x2 inch circuit board was shoehorned into a loco wherever it would fit, each loco was a different frequency so you could control up to 20 different locos at the same time on the layout without the complicated block control board. Obvious problem there even on a big layout was trying to control more than two trains at the same time, but when my four brothers and I had a "meet" at Dad's house that made for 6 engineers, and we found that two trains each was manageable so running 12 trains at once wasn't that difficult. Some AI controllers would have simplified that, and worked better for smaller families, so it wasn't long before Model Railroader magazine started several articles on computer control for layouts. Some people took it a step beyond and turned all the control over to the computer, just sitting and watching instead of controlling one of the trains themselves.
Not to my taste since I prefer driving a train myself, but it's easily doable in Trainz just by adding the player loco on an out of the way siding and switching to the #4 view without moving the player loco.