Installing drush for use with Drupal 8
Drush is an incredibly helpful tool, you are going to enjoy it. There are a lot of other benifits you'll get from installing it as well. 

I'm going to assume you are on a Mac.(There are other ways to do this on a Windows machine, but you'll have to look for them.)


Drush installation is independent of your Drupal version. The only variable is which version of Drush you install. This shows that you'll want version 8.x for Drupal 8.
Yes, your Bluehost server already has Linux, Apache, PHP &amp; MySql. The LAMP stack that is referred to in the digital ocean tutorial is one that you install on your home computer. This will allow you to work locally much faster than making changes locally, uploading them to your Bluehost server and seeing if they worked. I'd recommend using homebrew to set it up. Here's a great article to help you out.
Here's some info on installing pear on your Bluehost server.


As for the other questions...


No, you don't need the composer module. (I haven't used it &amp; I've been using drush for years. I'm not dissing the module, I just know it isn't needed.)
Try this go to see how to install composer. This will tell you how to install Composer on both your 


You haven't specifically asked about this but I hope you take the time to install LAMP on your home computer. It'll be a hassle but end up in a huge leap in your productivity. BTW You can also use homebrew to install drush. Here's a Drupal article that explains how. 

Good luck!