Mesh is the way to go. Overhead will be very light, depending on the material.
Upside is that since you are drawing them, you get to choose how they get-drawn (shader). This could be a boon down the road if you realize you need something else from them (color them based on some value, like if it’s colliding with something?); you at least get options from this step.
If you also set the visualization against some flag/value you can turn them on-off if you need to, at will.