When creating this I have just been using Auto Smooth with an angle set 30º - It seems to work fine. But I notice that you are also using Mark Sharp on the edges you wish to sharpen.
Do they work in conjunction with each other? If I only use Auto Sharpen is that OK or am I missing something here?
If it's working fine then stick with autosmooth. I tend to be picky / perfectionistic and thus choose specific edges for sharpening. But autosmooth is totally valid.
The only issue I could imagine is in the last video when I add a lattice modifier to stylize the overall proportions of the chest. That might introduce sharpening to undesired edges in the process.