Question: I've seen a lot of different topics and suggestions on aligning and inputting buttons/text, but the ways I've seen seem kind of risky.

What is the optimal way, for example, to add two buttons, stack them together, and have them be 10% from the bottom of the screen, and centered horizontally on all devices?

Answer: 
Use your Storyboard and add [Auto Layout](https://developer.apple.com/library/mac/documentation/UserExperience/Conceptual/AutolayoutPG/index.html) to your elements. Here is an example:
[![enter image description here](https://i.stack.imgur.com/gAQCd.png)](https://i.stack.imgur.com/gAQCd.png)

I have added auto layout

* Left
* Right
* Top
* Bottom

If I want to change the distance between the buttons, I just choose the auto layout constraint that I have created between the buttons and changes the constant value to it.

If I say that "Button 4" constant to the top shall be 40, then it´s always 40 no matter what size the phone has. If I change the constant between the buttons to 10 then it´s the same for all sizes.
For iOS 9, an even simpler Auto Layout approach would be to use [UIStackView](https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIStackView_Class_Reference/).

As you can see, no constraints are needed for the buttons embedded in the stack view, as the stack view lays out the buttons for you. All you have to constrain is the location of the stack view itself.

Here's an example of two vertically stacked buttons, 10% from the bottom of the screen, and centered horizontally for all devices.

[![enter image description here](https://i.stack.imgur.com/izHwx.png)](https://i.stack.imgur.com/izHwx.png)