Hex editors are very dumb tools and actually don't do anything particularly special. However as they show the whole files, can figure out location and have a basic text decoding (some having slightly more configurable decodings) then they are useful as blunt instruments or to show other hackers the contents of a file in a picture.
New hackers often seem to want to view as them as almost magical and something to learn when in reality they are anything but. Now learning to figure out file formats and relate it back to hardware, and what is otherwise seen. That is a bigger trick.
Or if you prefer being hot with a word processor does not confer you any great ability to write a novel. Same with hex editors and ROM hacking.
As far as finding the modelling tool then first make sure you have a need of one, and while some tools are annoying for legacy formats you might be lucky. Someone might have also made an import old version tool/filter/plugin (someone might also have made an import console format plugin if it is a commonly seen one or one for a popular to hack game -- nobody really cares about post 16 bit Sonic on the hacking front, and I am shocked anybody cares on the playing front but enough of my rants about Sonic Adventure).