Still learning, newbee P7

I grabbed a freebee Mat pose file for a hair prop. It was a simple color change of 2 sections of the hair. When I loaded it the base of the hair disappeared in the preview pane. It would render, just not show up in the preview pane. Stumbling around I see the artist used the trans map that came with the hair which was 1000 x 500 72 dpi and their revised color was 1333 x 667 x 96 dpi. I have to assume both files must be the same size, because when I changed the files sizes to match at 1000 x 500 72 dpi it now shows up in the preview pane.

Yes or No? I assume I could have done the reverse and created -duplicated the original trans map to 1333 x 667?

Yes or No? If the above is true, could increasing the transmap that small amount (1333 x 667 vs 1000 x 500)  increased the detail of the hair after it was rendered? The reason I am asking is the base the hair looks more course now after rendering.. Granted it could be the map that is courser.

On a side note I seemed to have read some where and I can't find it again, that changing an item like prop hair from an embedded geometery to a reference to an object file, makes the scene saved file much smaller, makes Poser more responsive in the preview pane since it is referring to a file external vs something that was loaded via an embedded geometry. I can't remember if the article mentioned anything about render time and render resources however. I have done this conversion on two hair props so I could run them through Wardrobe Wizard to fit another character. Is this a side benefit of that process or did I come away from what I was reading with the wrong impression? If this is ture, then I assume if doing this might help a scene where you more then 1 character in the scene. Or is that another false impression?

TIA