No doubt about "it would be more ideal..." I wish it will be that way too. This story implies that it will not. But while it's still one big ball of mostly vapor/imagination, we can easily imagine it will or won't.
With an M2, I wish it was basically a full Mac so I could pack it plus a bluetooth keyboard and mouse/trackpad for my ALT laptop concept. But all rumors seem to dismiss that possibility entirely for this version. It looks like Mac apps will need to be running on an actual Mac and Vpro can simply be a super-sized Mac screen on demand. Presumably that M2 is busy managing all of the stuff unique to Vpro without much spare horsepower to be a Mac too. I recall that copy & paste wasn't available on the original iPhone, so there will almost certainly be even some simple wants that are not there out of the gate.
As to sharing things from Mac to Vpro apps and back again, that too will prove desirable... and whether this "just works" or doesn't is to be determined. My guess is that there will be issues at the beginning that may get resolved as it becomes clear that Apple missed some wants that will manifest by many users.
Airplay 2 latency: all I could offer is fake it now to a television: MB airplay 2 through AppleTV to a TV. See what you think of the latency. My guess is that is a good approximation.
Since FCP runs on iPad, someone using a video editing app in Vpro might be using that app... or iMovie... or something dedicated for Vpro.
No idea about the physical drawing monitor concept.
And how reference images could be displayed, dedicated apps or Mac screen only, etc is all TBD.
To all of this, you can find out in a few weeks. You'll have a good list to carry in to a demo and see if it can do things you want to do or not. As is, there is a general concept that this can run multiple iPad apps at the same time. So anything we think of the we want it to do but don't know if it can could be roughed up in iPad apps. Conceptually, if someone has a current and older iPad or two, they have the ability to fake 3 floating iPad windows right there.
Then we have this "anything on a Mac screen" capability too... which I believe will translate to anything on Mac Screen SPACES, so that there is actually many Mac screens available with unique Mac apps running on them... but only a single screen view at a time. I suspect Mission Control with many spaces will largely work the same way as it does on a Mac now. So anything that works with Mission Control & Spaces probably works with a virtual Mac Screen in Vpro.