At the moment the Export action of the File Utilities plug-in create files from 96px (thumbnails) to 2560px (full screen size of a 30-inch "Cinema" display). This function was intended to export files for web/blog and email uses: the resulting files are optimized towards a good quality vs. size balance and are stripped of all metadata.
The Export function's speed comes from our codec's speed and parallel processing, as the batch file processor runs processing rules on multiple cores and/or multiple CPUs concurrently so it works on several files at the same time, depending on available processor resources.
Of course you could write your own custom action in JavaScript or VBScript and do whatever you want with the images: you get the source image's full pathname when your action is invoked so you could grab the file passed to your custom script and do whathever you like with it (for example run
DCRaw.exe to convert a raw file to TIFF or extract the embedded JPEG, or use ImageMagick's ActiveX object,
as exemplified here, to convert your input files to whathever required dimensions in about two lines of script code).
Icing on the cake: your custom action runs in the same multi-processing environment as built-in, native actions (provided by the File Utilitie's rule execution engine) so you get the same multicore speed boost for free, compared to serial processing
RELATED:
Using the Files Utilities plug-in (simple script examples at the end of the section).