addon.xml proper use of <res/>

Looking through the wiki, I don’t think I understand the best practice for defining skin resolutions. From looking at Estuary, I assume using resolution-unique named folders is deprecated, instead the <res/> tag should be used? Is there an advantage of using one method over the other? Is there a minimum number of <res/> options that should be provided? Does “width” and “height” take priority over “aspect”, or are both even needed? Anything else that should be known about resolutions? I assume it is now standard that default layout should be 1080-based?

scott s.
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