By and large you want to say what game you are playing and what system it is on -- make life easier for the ones you want to help you. I presume this is super robot wars alpha for the dreamcast, not that it particularly matters for the basic overview.
Game text does not have to be, in fact rarely is, the basic ASCII your hex editor might be decoding things as for convenience.
Finding and decoding the text (and surrounding information that makes it work) then becomes the foundation of text hacking.
https://www.romhacking.net/utilities/513/ is good for English and most European/Roman alphabet languages but Japanese has more limitations, or needs a lot more prep work.
mech modifier (assuming the mech is not composed of different parts, though that only changes things minor amounts) and pilots most likely falls under character selection cheats, that or level editor cheats if that is a thing for the game where fixed mechs/pilots are used on a story beat type deal (most of these you do get to pick but other times they are fixed, though fixed by map and fixed by menus not providing options to change and thus attacked by cheats are a different matter).
If you are interesting in text hacking
https://gbatemp.net/threads/gbatemp-rom-hacking-documentation-project-new-2016-edition-out.73394/ has a lot on it,
https://www.romhacking.net/start/ is also good. I don't know what we are suggesting for pulling apart dreamcast isos or as an emulator to use when debugging but romhacking.net above should have something.