External flow simulation mesh stuck at 0%

Well, your description is a good summary - it depends on the application.

For external aerodynamics, it’s definitely a good idea to keep the y+ under control. Surface refinement is interesting to ensure a smooth transition between the boundary layers and the rest of the mesh.

Furthermore, having region refinements for the wake is also a common practice. But of course, this can take some tests. E.g. here is a starting point: FSAE Tutorial - Preparing Simulations For Success - CAD Preparation

Cheers