The whole point of track lights is that you can exchange light heads.
In addition, you can move them around, and place them wherever is most appropriate for the settings of a perfect ambient light.
The trick is to make sure that you get the standard tracks and standard heads.
In the USA most of the standard tracks are neutral on one side of the track, and hot and ground on the other.
To be more specific, inside the track, there are strips of conductive metal. Most commonly, this material is copper.
The strips of copper, go from one side of the track, all the way to the other, transferring power to/from the fixtures and to/from an electrical box.
Now back to the question, are heads interchangeable?
The answer is: – as long as the prong system in the fixture matched the track, and you have the correct voltage in the track, it will work.
How Long Are The Tracks?
In the United states, tracks can be found in lengths of 4′, 6′, 8′, 10′, 12′ and less commonly found but existing in the market, 16′, 18′ and 20′.
These tracks can especial ordered to your project and specs.
Now if you are working on a run-of-the-mill project and just want to buy a regular track from your local wholesaler electrical supplier, the most common track dimensions are 4′, 8′ and 12′. Most likely they will only have white.
Everything else is special order.
Can A Track Be Cut?
Disregard the fact that every track comes with a horrible warning, saying that the track cannot be cut.
The standard track light is made in a way that cutting it, will not hurt the track. They list it in every track because you will lose your warranty.
Make sure that the metal shavings do not get stuck in between the insulator rubberized track in between the leads.
That mistake can cost you a whole lot of trouble.
Cut clean perpendicular to the track, and make sure that you install an end-track or a live-in to seal the end of the track and insulate the leads.
Those are insulators and they prevent short. Ultimately just follow manufacturer instructions if you are not comfortable doing this.