I'm making a modular system for a 2D spaceship arcade like game, the user builds their own ship with equilateral triangles to make more complex shapes. When the ships are small it's no problem, but as you make bigger ships you would have to add more bodies to the physics engine, so I think I should just combine all the bodies and make a polygon outlining the shape I'm making and simply render it as multiple. But I've also heard it's really computationally expensive to use shapes other than squares, triangles, and circles.
Tldr: I have a compound of triangles, should I just leave it as is? Or make a polygon outlining the overall shape? Which is better performing? Is there anything I'm missing?