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.
Your best bet is to use [Auto Layout](https://developer.apple.com/library/mac/documentation/UserExperience/Conceptual/AutolayoutPG/index.html). It takes a bit of learning but once you get used to it you can add constraints pretty quickly and easily in Interface Builder. I can't recommend any particular guide but there are a lot of good ones to be found with a quick Internet search.

Here is an example of constraints that seem to be what you are looking for:

[![Auto Layout Constraints](https://i.stack.imgur.com/JVDZX.png)](https://i.stack.imgur.com/JVDZX.png)
[![iPhone 4-inch Portrait](https://i.stack.imgur.com/K9SaD.png)](https://i.stack.imgur.com/K9SaD.png)
[![iPhone 4-inch Landscape](https://i.stack.imgur.com/YmzIQ.png)](https://i.stack.imgur.com/YmzIQ.png)