Camera Following the Player's Cube?

Use this(explains everything):

Camera Manipulation

On a more detailed answer:

You'll have to set the CameraSubject to the cube trough a localscript.

local player = game.Players.LocalPlayer
local camera = workspace.CurrentCamera

camera.CameraSubject = workspace.Cube

But if the characters SPAWN and ARE the cubes, I don't really think you'll need this. Unless you don't use the StarterPlayer's built in functions to handle such cases.

This will be useful for you.