Build Settings

I am new to Unity and I have a very quick general question. My main target for my game is ipad and Iphone.

Knowing that, when I start my game should I start building it with the IOS platform selected?

 

yup, if you want to try it on ios platform, playing it on ios platform and Editor won't have the same result.
BuildSettings -> ios -> put the output file .xcodeproj into xcode -> Product -> Build.

 

Just so I am clear...the first step I should do when staring to create a new game is to switch the platform to IOS, then create the game.

 

Yes, this is in general a good idea, although you can switch between build targets at any time. So it is not a crucial step.

Main advantages, as far as I can see:
- gives you some standard resolutions / aspects in game view (you can also add this manually)
- you can see easier what compiles if you use compiler directives and if you use plugins/services such as unity ads that need iOS/android
- no need to reimport assets when you compile for Xcode (whenever you switch build targets all assets are reimported, which can take some time)