> ... So the attendees for the session either see you, or they see the content: but not both at the same time.

No. With the correct configuration in OBS, they can see both - you and the screen. This is the latest video I have uploaded to demonstrate the visual effect I mean: https://www.youtube.com/watch?v=DgXhH5VK1pE

> Unless you run OBS in the virtual machine, and join the Zoom session from the virtual machine too, in which case OBS is unnecessary.

Hmm?

I run OBS on the Windows 10 host system. That system is operating at 1440p @ 165Hz. The VM is operating at 720p at 60Hz. OBS uses the VirtualBox window to represent the VM as a source. I then use my mirrorless camera (Sony A6000 via a capture card) as my "web cam", and green screen my self over the top of the VM window in OBS. I use my Rode NT-USB microphone as an audio source and then mute the desktop audio.

You can then use one of a few plugins for OBS to present the output of all of this as a virtual web cam, which can be presented to Zoom as your camera. Your audience then see your combined efforts in OBS all rendered together to produce something akin to what you see in the video.

But OBS then gives you another trick (among many): scenes. You can transition between scenes really easily. Here's another example: https://www.youtube.com/watch?v=P-409oJ9mBA&t=1h03m35s -- this example demonstrates two things.

Firstly that a green screen allows you to increase the possibility of eye contact with your audience by bolstering your size in the frame without having a rectangle of mess behind you (see the video I posted above as an example of what a green screen now looks like.)

Secondly with OBS you can use smooth transitions to move between scenes which can include stinger transitions, but more importantly those scenes can contain everything and anything. For example I use a could of scenes: one for really up close view of me as I talk to the camera and a focus on me is important; and a second scene in which the terminal/screen is important and I'm smaller and boxed into the lower bottom-right side of the screen (as seen in the first video), shifting the focus to the content and not me.

This all comes with a few key benefits...

Using a VM means I can use Windows for OBS and several other tools, but I can run Ubuntu/Linux inside the VM for the better tooling and terminal emulation.

It also means I can run the VM at 720p but my desktop at 1440p. Using a terminal/window in a 720p VM window is PERFECT for showing text in a console ("720p is the target resolution. In pixel terms this is 1280x720. We've gotten the best results when we record at 1280x720(HiDPI) mode, giving an effective visible resolution of 1280x720, but extremely crisp." - https://egghead.io/articles/recording-a-great-coding-screenc...), allowing the text to be very highly visible/readable without having to use zoom in features live or in post.

You can also snapshot the VM once it's in a working/desired state (which can be configured using Ansible in minutes) and then produce clones for use for different reasons. These clones can diverge off on a crazy tangent without you having to worry about losing the original (working) state.

You can craft the perfect development environments and even have them talking to each other on an internal NAT network inside of VirtualBox. So you can create networks of systems to demonstrate network connectivity issues, security or just the standard client/server model.

Using a VM also produces a better alternative to "Do Not Disturb" because DND cannot protect you from accidentally showing private/sensitive information live on stream when you alt-tab to the wrong window.

Ultimately use what tools and methods work for you. I've found that emulating high-end Twitch streamers meant that I could have a very high production value and loads of tricks up my sleeve for close to zero cost.

Hope this helps.

EDIT: I forgot I had this video I did on CI/CD for Chester University in England. It's a big download (sorry) but this is how I use OBS and the above to do university lectures: https://drive.google.com/open?id=1xT31CU8Lfob88FxaDXAVWy-uXC... (skip to about the 3m mark for the slides)