Its difficult to uninstall a DE and wanting it to fully clean up after itself.  Files will be left behind; configs, etc.  But for the most part it will be removed.

What you might want to try is to install the devuan netinst.iso and do not install any desktop environment at all, make sure to un-check default desktop.  This will give you console only.  Then if want X, install lightdm along with a basic window manager such as openbox.  This will allow you to install and use desktop applications such as a web browser.  Make sure you install a terminal such as xterm or lxterminal to make the window manager usable.  If you find this too basic, then install xfce or lxqt. 

You can get a much lighter desktop if you do not install via meta-package, instead install the individual packages (xfce4*, lxqt*) with --no-install-recommends.  But you really need to understand the components of the chosen desktop env to do this.

How do I know which packages are necessary?

What DE do you recommend for a netbook with 2 gb ram and a single core 1.6 ghz processor?

What if I want to get rid of a DE altogether and learn to do everything via terminal, what do I delete to accomplish this?

I am into emulation, reverse engineering old video games, and I'm an ok Java programmer. I'm somewhat clued in to this stuff, just never bothered to learn before. I might need I think X (?) to run an emulator and web browser, but I want to delete everything I don't need and cook my own tools when needed. Yes this is insane but I'm stuck with a netbook for now so I may as well optimize for it's limitations.

1. How do I change my desktop environment (xfce, lxqt, etc)?