We know that generally textures have to be square with a side that is power of two, in order to leverage texture compression (DXT, PVRTC etc). But does this stands true for sprites when using Unity’s 2D system? As I understand, all sprites are repackaged to the atlases during build by Unity, and that atlas probably has correct dimensions, so Unity is able to apply compression.
So, the question is - am I right and it is ok to import non power of two sprite sheets? Are there any downsides to this?
Your are missing the point about atlasing. All sprites are repackaged to atlases during the build (by default), so obviously they’ll have correct dimensions after that, even if that can’t be seen anywhere in the editor.
Only if you have Pro, and have enabled automatic packing for those textures.
Sprite sheets, no…those should be power of two. Individual sprites can be whatever dimensions you want as long as you have Pro and are using automatic packing. If you don’t have Pro then you should most likely be making atlases yourself, which you can slice using the sprite editor.