Blender meshes,does size matter?

My current question is simple.
I design…say a rock of what might be 5 feet in real life, but to blender units,it may be 20 feet, so if I go into Unity and CHANGE the size to fit,so no longer 1,1,1 it may be .3,.2,.3 does this TRUELY matter? Or should I learn to model EVERYTHING in perfect size in Blender then import to Unity? This questions been on my mind lately. Thanks for any help!

In fbx import settings you have an option called Scale Factor. Having a non uniform scale will not affect performance or cause problems with colliders. Say you have a cube and set it’s scale to (1, 15, 1). You’ll be fine.