>> So in essence we need to change the settings in the computer's registry to save high resolution images in Windows? Is that correct?
Not entirely. Have a look here: https://pptfaq.com/FAQ00052_Improve_PowerPoint-s_GIF-_BMP-_PNG-_JPG_export_resolution.htm Among other things, there's VBA code there that you can use to export at any resolution up to PPT's limit, which is quite high nowadays.
The code works for Windows PPT, might need some adjustments for Mac.
PPT won't export images with an alpha channel (ie, with transparency) but you can open the exported images in any decent image editing program and resave with transparency (IrfanView is free from irfanview.com and does a nice job of this).