PokemonGameEditor VS poryscript

this would be super easy to do, even if you don't want to get into the newer more complicated stuff like decomp, there are plenty of older tools out there like Pokémon Game Editor and Gen III Rom Hacking Suite that would work just fine if all you're doing is changing names of Pokémon, moves, items, trainers, etc.

Download Page Link: https://github.com/Gamer2020/PokemonGameEditor/releases

editing pokemon data should also be fairly simple depending on what you want to do. for this i recommend pokemon game editor. it has a variety of functions, but you can load your rom and pick the pokemon editor. pick the species you want to edit in the top-left. the species' catch rate is in the base stats tab, next to its other stats like HP and attack and so on. you didn't mention wanting to change evolutions, but that should also be really easy, and it's a popular edit in case you want to get ride of trade evolutions. just go to the evolution data tab and change "condition" from "trade" to something else like "level".

scripting is something i have a lot less experience in, both in binary and decomp. from the little scripting i've done, writing in poryscript seems a lot like writing in binary script languages, except that you don't have to worry about offsets and free space. i think this is the main difference you'll find if you only make simple events.

porymap, a map editor for pokeemerald, has a mac version, and so does poryscript which is a script editor. for anything else, you don't need any extra tools at all. you'll edit pokemon base stats in any text editor, and graphics in any image editor.