I've been reading but couldn't find an answer to my question:
If I have an object, let's say 30x30. Should I use a texture that is 30x30, 300x300, or even 3000x3000 or should I follow 'the powers of two' for textures?
I've been using 3000x3000 for a 30x30 object and it has been working, but I'm worried that it might not work for others.
Depends on what you do. For a 3D game you have to test it in practice - if it looks good when the camera is the closest - then the size is fine (you can even try to decrease the size of the texture to save memory/bandwidth). For a 2D game (orthographic camera) having textures in the same size (in pixels) as they appear on the screen might not be a bad idea but it all depends on your 2D camera settings and target device(s).
Btw, you know that Unity changes all textures' sizes to powers of 2 by default? It improves performance (at least on some devices) and from my experience it doesn't decrease the final images' quality. So I guess, unless you have a concrete reason to do otherwise, you can just stick to that.
3000x3000 is 9,000,000 pixels.
300x300 is 90,000 pixels.
30x30 is 900 pixels.
It all comes down to how much 'art' you want on the texture. I would use the smallest resolution needed to get your art to look correct at its optimal viewing distance from the game camera.
You also want to think about memory considerations. A 30x30 texture takes up less space than a 3000x3000 texture.
It's also good practice to keep textures as a power of 2 if you're using Unity as Unity will do its own compression to make it a valid power of 2 texture.
You should always do 3D textures in powers of 2. Just because of how video hardware operates, it is more efficient for them to deal with image dimensions in powers of 2; in most cases this processing difference won't be noticeable, but for complex graphics these little things can add up.
