1. I also often use aven to assist my drawing. What helps me alot here is linux/kde, because I can do stuff in aven, put the window below xtherions and make the xtherion window transparent. Aven works as a kind of „background image“ in that regard.
Now that is a really useful tip! Shame Windows still seems to lack that feature, and every app that can do it is either abandonware or domain squatted, or an unsigned download from a dodgy site.
2. when drawing vertically, isn‘t drawing (and rendering) exendet elevations far more useful and expressive? You also can export xvis in that projection.
For a vertical cave, almost always! For a vein-based mine, not really, since you want to preserve the relationships between levels, because the standard view is a cross section through a mountain, and they regularly join each other. Projected elevation can often be best there. But I think Jean-Florent's question is almost certainly about drawing the plan view, which is a nightmare when everything overlaps everything else.