The Bevel shader is a normal shader and simulates microbevels at the edges of a model: https://i.imgur.com/dD4T9KQ.png

The Mecabricks addon for 2.80 supports the Bevel shader and will use a radius of 0.35. The Samples define the bevel quality. You will recognize the fake-bevel when you get very close at the edge of an object. The Bevel shader is perfect to save unnecessary geometry. At a normal scale you would not see the difference. The technology is originally patented by the German company Mental Images which was acquired by Nvidia in 2007. The shader is implemented in most of the renderers like Mental Ray, Arnold, Redshift or MODO. The Blender dev team developed a different method to get around the patent.

I recommend just to use the 2.79 daily builds. We are using them in production all the time and had no issues. I personally keep always two to three versions just in case a daily build needs to be fixed for the next day. So you can use the former version without the danger to lose data or a scene can't be loaded anymore.

Actually I am using for Mecabricks renderings 2.80 all the time. I don't think I will go back to 2.79 again.

If you want to stick with 2.79b and the shader is available in this version you just need to look for the Rounded Edges OSL shader and replace it with the Bevel shader. The OSL shader will just support CPU rendering and is much slower. I had modified the Template scene in the past by adding the Bevel shader to the materials and save my own Template scene.

@Renderbricks Thank you for your explanation. So - let me know if I have this wrong - you're saying that I just need to look for the Rounded Edges OSL shader in Blender 2.79b and then replace it with the Bevel shader? If so, how do I set about accomplishing that? 😕

Blender 2.79b doesn't include the built in node called 'Bevel Shader'. It is only available in Blender 2.79 daily build and 2.80
In the past, a Blender user developed its own script to simulate this effect. This is used in a custom node as part of the materials in the old free Mecabricks add-on 2.0.7 as well as the advanced add-on 1.1.1. The drawback is that it requires to activate OSL which only renders on CPU.

If you don't get a word of what I just wrote, I would recommend to download and use Blender 2.80
https://docs.blender.org/manual/en/latest/render/cycles/nodes/types/input/bevel.html