phpthumbsof, phpthumbsup, phpthumbon and friends use the default MODx phpthumb library, loading it if it's not already loaded by MODx (core/model/phpthumb/).
Well as a follow-up, I am still unsuccessful at targeting the first row of the template.
Working with FileLister, I can apply a first row class, but also need to generate a different sized thumbnail for the first row. Although apparently phpThumbON can use the IDX modifier, I was not able to get phpThumbOn to work at all. Installed it, changed all my snippet calls, had error messages telling me it could not generate a thumbnail and could not create the cache file. I suspect it had something to do with paths and the fact that my image files are outside of the webroot, so I took a stab at changing the system settings to paths that I thought should work, but no luck. With most of the documentation in Russian I just ran out of debugging patience and uninstalled it.
Next I installed pThumb, which had trouble finding ImageMagick. I changed the system setting to use Resizer and that seemed to fix things. pThumb does not apparently care about an IDX modifer though, so although I feel it is noticeably faster than phpThumbOf (totally unscientific findings), it has not gotten me any closer to my goal of creating a different first row template.
I also tested FileDir in place of FileLister, it DOES take a +FIDX modifier, but unfortunately has trouble sorting; gets buggy when you apply a sort order and applies the IDX 1 to any row it feels like. (Actually I think it applies it to whatever was the first row before the sort.)
I am giving up (for now) with this problem only half sorted. Thanks all for your help.
☆ A M B ☆
☆ A M B ☆