[Testing] X11(simple desktop) + Chromium(web browser) in a simple installer for Stretch

I have a question I installed VNCServer using this link

[[HowTo] Install a vnc server on the Raspberry pi]
([HowTo] Install a vnc server on the Raspberry pi)

Works great so would I need to install another window manager or can I use the one installed to support VCNServer?
or am I wrong and he VNC_server isn’t using xwindows at all?

Second question
If VNCServer uses a Xwindow manager and you can use the xwindow items that support it is it possible to switch between Kodi and chromium using virtual windows or something similar to alt-tab?