New answers tagged mobile
I can't speak specifically for Unity, as I don't use it, but based on my understanding of graphics hardware (I have written a multi-platform 2D rendering engine or two), there will be no performance overhead using non-pot sections of a pot texture. I can think of no reason why this would be any different for Unity. The overhead is purely hardware based.
A class is a chunk of code that can be reused as an object. An object is a single instance of something that can have certain properties (e.g. an integer representing a characters intelligence or money amount). Now that we have that settled... Going light on object creation and heavy on object reuse is generally better. It uses significantly less RAM to ...
If you're just looking to make your game compatible with some older devices consider using Quality Settings . Go to Edit->Project Settings->Quality Settings to set up each level and instruct Unity to use full size textures/half size etc.... Then add a Menu Scene that will load first allowing the User to select the settings he wants for his devices.
Top 50 recent answers are included