So, I wanted to draw Changelings and differences in their sizes.  
How I headcanon changelings (And to remind, this is my headcanon only, you are free to disagree):  
I figured Changelings would mirror bees and ants in a way that drones might be smaller while soldiers are somewhat taller, thicker might be an option? Queens would of course be tall and imposing.  
Personally I headcanon that changelings are capable of taking forms of both stallions and mares because they have both “equipment”, but might not have as strict of a concept of gender, or it is fluid. To some it might be personal preference.
 
Considering weapons and armor, I think they’re made of hardened changeling goo (like the goo that trapped Celestia in Canterlot wedding) that hardens when exposed to air and can be sharpened, looking much like glass, except less prone to shattering?
 
It’s not probably very new headcanon, but eh. Felt like sharing.  
Also yes, the hair-idea did come from Farrah Fawcett.