Batch video conversion from command line

Hi fellow sailors,

i have lots of downloaded... ISOs... that i need to converto to save space. I would like to make them all of the same size, let's say 720p, and same format, let's say h265.

I am on linux and the... ISOs... are sorted into a neatly named hierarchy of sub-folderds, which i want to preserve too. What is the best tool (CLI) for the scope? I can use ffmpeg with a bash script, but is there anything better suited?