I just use 'Auto-fit' and 'Letterbox Scale'. However, for the best fit, there is a lot more discussion in other forum posts (especially with regard to newer iPhone notch and scaling.)
In terms of permissions, my game did not need any additional permissions, because it was not using services or camera (just single player experience without sign in or leaderboard.) Of course, you need the usual Apple certificates and provisioning profiles to deploy to a phone or Test Flight or the App Store.