That reminds me, can Nintendo's own line of emulated GBA NES ports be documented? This is probably something that never gets talked in the romhacking/emulation community.
You never actually see how the emulation works in NES to GBA ports, you know, like how the music compares to the source, how the colors look compared to the NES colors, why the resolution looks so weird, or why oh why does it look so streched out.
The only hacks I've seen done for the Classic NES Series/Famicom Mini GBA series was a translation for a Super Robot Taisen game, and the famous Easy Ring from Mato's Mother 1 (from Mother 1+2) translation.
Is like the Classic NES Series/Famicom Mini GBA series of games are the black sheep in the world of romhacking. That's why you don't see a lot of documentation from those games.
A few people did delve into them, I recall a few threads on the now sadly defunct pocketheaven forums. For the most part though people write them off -- nowadays emulation can be done just fine on most things, and even back then the likes of pocketnes and HVCA offered superior experiences by most accounts. Also a few people did hack NES games to work better with said emulators, a site called GBAfan used to house them.
The reason they look stretched or odd tends to be because the GBA resolution was lower http://problemkaputt.de/gbatek.htm#gbatechnicaldata
("Display 240x160 pixels (2.9 inch TFT color LCD display)" than the NES ( http://wiki.nesdev.com/w/index.php/Overscan
256x240, give or take a few other things). The GBA was not quite potent enough to do proper scaling on top of emulation so you either crop/letterbox or do something called a tile crop where you lose pixels from each tile (many of those hacks I mentioned were to redo fonts to work with tile cropping, indeed one of my very first brushes with hacking proper was to do Final Fantasy 3 translation font to work with it). Edit managed to smack wayback machine into spitting up a copy https://web.archive.org/web/20061101111343/http://gbafan.com:80/rom_hacks.html
In the case of a port/emulation most hackers seek to work on the best version of a game, and failing anything interesting happening there the original one is the one which is picked. The GBA ports of various Final Fantasy titles are probably the only real exception to this.
Pull them apart if you want (though I reckon that protection stuff I linked earlier might get in the way a bit) but again without the incentive of a good fix you can't otherwise easily replicate, an official translation where there might not have been one before, or been a weaker one, or possibly be a good candidate to inject other ROMs into (N64 emulation on the GC was a fair technical feat, hence the desire to inject other games into those but again on the GBA we saw pocketnes and HVCA, then it seems like the sort of effort that is better spent elsewhere.