One needs to be a bit careful here.
The illustrations in the Leiden MS (I assume it is Leiden Or. 289) are most probably derived entirely from other manuscripts (and those from other manuscripts), so the link with nature is quite remote.
For the Voynich MS we don't know for certain, but no earlier manuscripts are known from which these drawings may have been copied. A link with nature is possible.
With respect to style, there are several aspects that play a role.
2D vs 3D. (are we looking at a flattened image, or are certain elements behind and partially hidden by others?)
Symmetrical or not.
Squeezed aspect ratio or not.
It is not unusual for a single MS to have illustrations in several different styles. This is already the case for the Vienna Dioscorides. A very good description of these various aspects can be found in the 1974 publication about the Carrara herbal, by Felix Baumann (in German).
The Voynich MS clearly has some 3D aspects. You are not allowed to view links.
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Many illustrations are not symmetrical.
I have not seen examples of squeezed illustrations. These are typical for copies where not enough space was available, such as the Naples Dioscorides, and some of the alchemical herbals.