These issues are not theory. They all contribute to the performance of the arm. Whether or not you can hear the difference, frankly, means nothing. With any one issue you may not be able to discern a difference, but put them all together and you are more likely to hear a difference or not. Some people's hearing is more influenced by what they see then sound waves in air.
I can not play with or listen to every tonearm on planet earth. So, I have to pick and choose based on the arm's design and reputation. I am more likely to get an arm that works well by paying attention to design principles.