I drive a car with manual transmission. When I see from far that the traffic light is read, I shift to neutral and let the car role until either I apply the brakes.
The question I have is: Is this the proper way to drive or should I leave the car in gear until I apply the breaks and shift to neutral?
It all depends on several things. Overall it is generally considered a little safer to leave it in gear. The difference in safety is not IMO very much. However I find it easier to leave it in gear and for my car, it usually means I gain a little mileage. This is not true for all cars.
Overall, it is not worth worrying about.
The proper way (or at least how I learned it) is to leave it in gear until you’ve just about come to a stop, but realistically the only drawback to your way I can think of is that if the light happens to turn green, it’s kind of rough on the clutch to re-engage a high gear from idle. But realistically I don’t think the fuel savings from coasting or increased clutch component wear is going to be even remotely measurable either way.
I also do this when the path and sequence of events is perfectly clear.
One rule here. If the six year old in the back (booster) seat is not complaining, you aren’t hurting the car too much. There are some exceptions, of course, but that (your question) isn’t one of them.
Do not coast in neutral. You do not have full control of the vehicle doing this. Downshifting as you approach the light is the correct method and it’s safer.