About mods vs data packs

Hi folks,
I have zero experience with data packs, to be honest I did not know they existed until I stumbled onto kanokarob's channel 2 weeks or so ago. But the possibilities seem intriguing!
I do have modding experience, in fact it is basically how I learned programming as a kid. Currently working on a mod again for the first time in many years, and it boggles the mind how much has changed (and how much I have changed, lol). I wonder about the differences in the capabilities between mods and datapacks. What can one do that the other cannot? From what I can see in kanokarobs videos, you can do a whole damn lot with datapacks!
As a sidenote but somewhat related, if I made a custom generated structure using datapacks, how difficult would it be to later incorporate that same structure into my mod? Is it just a matter of taking the .JSONs and registering them in my mod, or are there fundamental differences to consider?
Well, thanks!