I have a notebook that's mirrored to a ceiling mounted projector. And I use multiple desktops on Windows 10 to switch between applications if I'm doing more than one thing. I usually go from memory, but have a printed copy of what I'm demoing to fall back on just in case.
Also have Adobe Connect running so that students can mirror my screen to their screen. Computers are setup so students are facing either a side or back wall so being able to mirror keeps the from having to bend their necks.
I record a screen cast and upload the video so they can come back to it later like notes.