It would at times take an expert in a given field to bring out the most in performance of things technological. This could be due to the very thinking feature to technology and its application that there is no single way of doing something. It is more a preferred way to proceed. It would come as no surprise that there are always different ways and methods to doing something that could be at times rather revolutionary in nature.
Separating mail boxes
It is a good idea to separate mail boxes and to keep a separate one for the mails that can be marked as spam and the not so important. This step is bound to increase the speed of access of the main mailbox as there are fewer files to organize each time. It would lead to a more efficient indexing too.
Avoid the use or iOS on 3G or 4G services. It does help to limit the usage of the phone with the background data enabled. Not only is the data traffic going to increase, it would lead to a shorter battery life at best. The better idea is to use 3G/4G services in short bursts to update the mail and such offerings than to keep it on perpetually.
Using control center
With the more recent iOS devices, there is a control center that is meant to simplify access and remembering of the most commonly used applications. This feature has the added feature that it would compromise the operational ability of the phone if a large number of applications are brought into the center. It is best desired that only the most essential of apps must be handled from the control center to present a faster operation of the OS.
Automatic updates are a convenient feature to have around that does away with the need to constantly update the system files and any application. Unless absolutely necessary it might be advisable to disable this particular feature as it could reduce battery endurance as well as slow down the system a great deal. It would be a good practice to have just the most basic of features put on auto update to bring in the best performance.
It is possible to have a UI that is flashy and more presentable as well. This would affect the operation of the Apple phone to a great deal and is best avoided. Unnecessary extra effects must be kept to the basic minimum at all times.