Sorry to be late replying. The simple answer is "no", because the render export will always use the larger value for the larger map edge in a rectangular JPG export, and hold the other to the correct proportion accordingly.

This may mean having to switch the orientation before printing, depending on exactly how the image is to be printed, but when creating just the image file, that's irrelevant.

I always put the same value in both, because it save me worrying about which edge might be marginally longer in some almost square maps, or (and this is more likely!) me entering the wrong value for the obviously longer side because I forgot which box was which in the export pane!

I tried a couple of tests using the "Save As... - Rectangular Section JPG" option in CC3+.

Ordinarily, I use a small amount of antialiasing on JPG exports, generally 30% to 35%, and forgot to turn that off, which meant the export failed! So I tried again with Antialiasing turned off.

I suspect the single key thing is to ensure the final export size is set to for A0 paper, so I turned that up to 119 cm. This is my settings pane:

And then I ran the export. The final file size is about 66 MB, but this is a sample zoomed-in to be 100% and then resaved as an image the Forum will accept (so it's smaller than the true 100%). However, when I was zoomed-in at that level, there was no pixellation whatsoever on the roads. This is that smaller image, but using the above settings:

I think all you really need do is ensure the final image size matches the paper size you want the export for print to be - A0 in this case. Good luck!

Ah, don't worry over it! The physics of crater formation is endlessly being revised and experimented with, like most sciences, whenever something new and unexpected turns up. It's a particularly tricky field, because most of the impact craters easiest to examine in some detail are on the Moon, which isn't a helpful analogue for such craters on Earth, or other places where there's an atmosphere to alter how they look on various timescales, from original impact onwards, or how they can form when an impactor strikes a medium that isn't lunar regolith and rock. First approximation stuff is fine to give a crater that looks like a crater non-specialists can recognise and make use of!

Plus, what you have now will work nicely for both impact and (inactive) volcanic craters - though the latter will work best connected to a suitable mountain-top or area of suitably craggy rock, of course.

So far as I understand it, if you have an MS Office 365 sub, Publisher will cease working in October this year (I think - can't actually recall the exact date now). If you have Publisher on a computer that isn't connected to the Internet (so it was purchased years ago, probably on a disk of some kind - 3.5" floppy or CD-ROM), you should be fine.

I checked around earlier this year when this was first announced, and it seems that the free Libre Office suite (essentially the free equivalent to MS Office) will still open MS Publisher files. I haven't had time to install and check this as yet, but I know the earlier version of their MS Word-equivalent worked fine, and would open MS Word documents, although MS Word (of course...) won't open their files.

I like Publisher because it's so easy to resize the physical page size to fit whatever you're creating exactly - so it's really easy to create and save images, including images drawn in Publisher, to a very precise size. I know you can do this in other programs as well, but I've been using Publisher for decades, so it's much easier that way. I used to create all my maps and diagrams using it 20+ years ago, including for print publications!

GW are not noted for their generous licensing terms; very much the reverse, in fact, judging by conversations I've had with owners of small businesses interested in trying to sell their physical products over the years, and they insist on a huge amount of control over exactly what can be sold, how much stock the business HAS to take per month (regardless of what the business itself knows will actually sell), and how it can be displayed. I can't imagine they'd be any more willing to consider something like this. If they were interested, I'd expect they'd be doing it in-house already.