It sounds as you want to evaluate different Linux Distributions.
DE/GUI is a good one, terminal commands is a bit useless since the vast majority of Linux systems use Bash as default.
This is what I would look into on a new distro:
UI - What DE or WM is it using, what is the default config like, and try to learn from that. How is the terminal prompt configured (the default Ubuntu and Debian prompts are terrible, I allways change them)
Package Manager - how does it work, what software is available?
Unique software - Does the distribution include some tools, applications or games I haven’t heard about? If so, what do they do, and how do they work.
This gives me a feel for the distribution and how to use it.