Hey,
I want to create almost primitive like vehicles inspired by GeneRally (I don’t want to do 1:1 copy, I want to do something similar, be able to experiment a little bit)
I don’t think there’s a rule or best practice for this. I would start with primitives. Merging and substract meshes. Then, where there’s a mesh you cannot work with primitives or polyhedra, draw the mesh.
I believe it’s mostly a choice of design. If you want to keep with some sort of consistency in your design, you should try to select a base of shapes and stick to it. Else, it will look like its lacking design/consistency.
Did you check out ‘art of rally’ new release? It’s less minimalistic but I personally love this design. Sort of a fairly realistic minimal design. There’s a great work of consistency/art direction done on this title.
I’d suggest same as @mawa
But if you want to take it to the next level, one of the greats of low poly modelling is this guy:
Especially take a look at this fantastic tutorial Learn Low Poly Modeling in Blender 2.9 / 2.8 - YouTube
And this Let's Make 10 CARS in 10 MINUTES in Blender 2.82 - ep. 12 - YouTube
I would like to close this question but I it would be great if anyone from the BabylonJS team could give some thought about it 
@GeneralQuestions
Depending on your skillset I would either chose the blender way, or the procedural way and do everything with maths and procedural shapes.
Thanks. I have no experience with the Blender so the answer is clear
