This might be considered somewhat petty. But just a personal choice.

Does MW record it's size and/or column widths in library/upload window?

My impression is these things are not recorded. Probably most people enjoy both the presets and the way the columns have a pulling factor on neighboring columns when moved. Personally I like to be abe to adjust them to custom widths. The upload window for example, the file name might be fairly long which means I need to stretch the column to see the entire filename. Remote pieces helps me to know how much of the file has been downloaded, but the full details are often obscured by default (probably for the large files.) It would be helpful if I could shift the column widths to a preferred width and remain that way between sessions. Likewise for the width of the gui. But obviously adding custom size options means recording the settings and potentially means slowing things down if custom settings exist.