OK, maybe try this.

1) Set up a suitably-sized snap grid that'll let you draw squares of the exact size you need, and keep the snap grid turned on.

2) Draw an outline square of the size you require, with the line thickness you need it to be, using the snap grid.

3) Copy that square, and paste it immediately below the first one. Again, the snap grid is your friend.

4) Then paste another line of two squares to the right of the first two, with the half-square offset required. You may need to adjust your snap grid to allow this correctly.

5) This gives you a base of four squares in the correct pattern that you can then copy, making a larger area of squares with the necessary offset. Depending on how large an area of squares you need, once you have a larger part of the pattern available, you can simply copy said larger number of squares to speed things up. If you group the batches of squares too, that will make copying the groups easier.

6) Once you've filled the area you need with the offset squares pattern, save this as your base file that you can then open and re-save each time you want to draw a map using this offset grid.

By using the snap grid and basic commands like grouping the areas of squares, the whole process should be pretty quick to do, and hopefully fairly problem-free.

[Edited this where boldfaced, as I realised after posting that the pattern actually needs a four-square group, not a five as I originally suggested! (Otherwise you end up repeatedly overlapping the column with three squares in it.)]

No, I'd agree with that too @Maidhc O Casain, although to my eye it's the very strong drop-shadow on the title that's causing problems, as I don't struggle with specific colours.

You may be able to get the roads more obvious simply by widening the lines, and maybe increasing the glow effect on their edges. The pale colouring actually seems fine.

I very rarely use any of the forest fill tools, since trying to get the tree-density right if your map's not a typical size for the style takes too much time and effort for me. Plus I usually want to add features in the woods, so end up moving or deleting trees to accommodate them. Thus it's quicker and easier for me to just place trees individually!

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!