MacOS – Make macOS look like a Linux desktop

Set up your new User as a Sharing Only account, this gives them no actual account on the computer itself that they can log into…

System Prefs > Users & Groups

1. Click the lock
2. Click the + sign to add a new User
3. Set the new account to sharing only from the drop menu [stepped out on the pic for clarity]

Ref : Apple KB - OS X Yosemite: Create a sharing-only user account

After Comments...
Apparently, this works, but only in combination with some other tweaks.

You need to set up a new group, 'remote users'.
Add your sharing only user to that, then add that group to Remote Login

It seems that Sharing Only users by default have the shell /usr/bin/false and the home directory /dev/null.
Both of these values seem to be magic values for some PAM modules to block the user from connecting.
You have to change both and have the user added to the remote users group to make it work.

I'll take your points in order:

• You can assign entire applications to desktops, but I don't know of any tool that can assign specific windows to desktops, at least out of the box. Maybe you could whip something up with Hammerspoon and Lua scripting.
  _{I've never actually used Hammerspoon, I've just heard about it. If you decide to go this route, good luck!}

• That's not actually how you move windows between desktops. That dock menu is for the entire application, not the specific window. (Windows actually don't even have window management menus at all!) To do this, grab the title bar and press ⌃← / ⌃→ or do a 3- or 4-finger trackpad swipe, or hold the window at the edge of the screen for a moment. You can also move windows between desktops with "Mission Control", a combination of Expo and Scale. You get to that with ⌃↑ or a 3- or 4-finger trackpad swipe up.

• It sounds like you're talking about fullscreen, not maximizing; it seems to just work that way. Unlike in Unity, though, the window no longer belongs to any desktop -- it's in its own space, all by itself. You can drag it between any of the other spaces, of course, if you want it over by the left again.

  • If you want to maximize your window instead of fullscreening it, ⌥ (option)-click the green_{(by default)} title bar button. Note that in some apps, like Pages, this will expand the window to fit the content instead!