Can I vertex paint in eevee or is it a cycles thing only? I would like to make some meshes that are deformed and paint the vertexes to created a nebula of light in a volumetric of colours and was looking to vertex paint in blender 2.83.4 but do not see any options for it, only texture paint.  I do not see an option to render vertices of a mesh only.  Is this only a cycles-renderer thing?
Select any mesh.
Press CTRL + TAB
Choose 8 (Vertex Paint).
Cycles also cannot render the vertices of a mesh directly. You can use a Point density texture. Volumetric effects in Eevee are fairly limited, I would not suggest the approach via vertices as a volume.