Does anyone has any suggestion regarding: How to reduce size of Unity games?
Something like what packages are really required, what are not, when camera should render etc.
- remove everything, add only when its required (even builtin packages)
- use build report tools to check what gets included in builds (and their sizes)
- use profiler for checking performance
*for advanced workflows (to optimize performance and file size), see inspiration from
Camera rendering has nothing to do with size. 
Generally, the less you put into the game the smaller the build size.
And then it’s down to figuring out what are the biggest assets (most commonly textures, sometimes audio) and then optimizing them, eg compression and other settings.
Analyze and improve.
Which compression would be efficient for audio, mesh, sprites, textures, build etc. in a unity project.
My goal is to make a game size as low as possible for better performance in any device.
All depends on target platform and requirements and what kind of game it is.
So you’d have to optimize per device,
for example: it might load different assets for web or mobile (and different shaders, texture resolutions, LODs etc)
Actual game build size doesn’t necessarily mean better performance.
Furthermore, some settings are not available on some platforms. For instance, if I recall correctly, WebGL and mobile platforms do not share a common texture compression setting.
Best advice is to build your game and profile often. Unless you actually get to the point of publishing the game, all of these considerations are rendered moot.