How can I create a series of objects that trail behind a player cube, and have collision detection?

(i havent used trail renderer yet so this is my suggestion)

if you are making a snake clone, i would imagine it would be possible to create a series of cubes, and instantiate them as required, then just set them to move at the same speed as the player. you can create waypoints when the player changes direction so that the following cubes can also change direction when they reach the waypoints.