The reason for the extra steps was that the Render Preview mode did not look the same as what I saw in the render window, but it was close enough for things like evaluating the position of sun and shadows. Later I found in documentation that the preview does use the RPR engine not Eevee, so the difference may have been due to incompatible nodes or materials in the scene file that were getting baked during render but not preview, not sure as I'm relatively new to Blender + RPR.
Off-topic but related to above: all of the scenes I can find for real world testing are built for Cycles; it would be awesome if AMD built a page with a few different test scenes where everything in the Blend file works with RPR (uses Uber Shader etc). Most of the downloadable items in the guide are very simplistic / not something on the level of a typical archvis or other complex scene with a variety of lights, surface material types, shader instances, etc.
Going back, I looked into this crashing more and I believe now this is a known Blender bug, specific to macOS. To be more clear, at Step 4, on the occasions where things crashed I believe I was jumping back to the Material / Shader preview mode in the viewport. According to the bug info, that specific mode seems to cause the crash, whereas jumping back to Solid or Wireframe mode does not crash the app, all else being equal.
It is better. It doesnt crash but it renders out glitches.
2,6 GHz 6-Core Intel Core i7
16 GB 2400 MHz DDR4
Radeon Pro 560X 4 GB
Intel UHD Graphics 630 1536 MB
eGPU radeon 580