Which is the best, and why?
Which is most lightweight and non-resource intensive?
Which is most reliable?
Are there supported risks or suspicions of any in particular being botnet?
Optional: Rank them from best to worst.
Is the following statement true or false (and state why): "Only Dolphin can display large folders of files in a reasonable amount of time."
Noob question: What exactly is the difference between DEs and Themes?
MATE is great if you want functional and lightweight
KDE
Why do people say Deepin is spyware?
>Which is the best, and why?
There's no such thing. Each DE has its own goals and caters towards a specific audience.
>Which is most lightweight and non-resource intensive?
LXDE. LXQt and Xfce follow close behind.
>Which is most reliable?
Xfce. It's as stable as it gets.
>Optional: Rank them from best to worst.
Not every distro implements each DE equally well. Based on my experience with Fedora (and my taste):
Xfce = GNOME > Cinnamon > LXDE >= LXQt > MATE > KDE
That doesn't mean KDE is bad, just that it sucks on Fedora.
>Is the following statement true or false (and state why): "Only Dolphin can display large folders of files in a reasonable amount of time."
No. Thunar and PCManFM both handle large directories incredibly well.
>Noob question: What exactly is the difference between DEs and Themes?
DEs are software collections, with the goal of handling your basic desktop needs. Themes configure how something (e.g. icons, windows or cursor) looks.
based
This. I thought it was a meme?
It is. Deepin is fine.
Deepin is spyware.
gnome
it just werks