Are more expensive chains/casettes more quiet? If we ignore the lower end products and compare mid and high end products. Is there a noticeable difference between the sound produced while pedaling in the same gear (Not the shifting sound)?

For example if we are talking about shimano, compare tiagra or 105 vs ultegra or durace.

This question is not so much for road use but to use the bike in a trainer inside a flat.
I think a well-adjusted, modern system from any of the major players in components will be reasonably quiet and generally the same volume level. The trick is to make sure your cable tension, limit screws, and derailleur alignment are tip top. But that's true even if noise isn't an issue.

In your case, I would guess that your trainer will be much louder than your drivetrain.