How to use Droplist types in Sitecore template fields

Answer 1

I would proceed exactly as @Trayek suggested in his solution. To expand on that, this should be your implementation:

You create your own template, maybe called CSS Class, and you will add a Single-Line Text field to it, maybe called Value. You will put the actual CSS classes in that field when you create the items.

Next, you will add a folder item somewhere in the Content tree, and you will add your CSS Class items to that folder. That folder will also be the datasource of your droplist/droplink.

To set your datasource, this blog post should be of help. You will be looking to use number 1 under For Fields without Search (screenshot included, below). I wrote the article a while back, so if you need any additional help just let me know.