I've got mine as the best form-factor emulation station (for older games) you could imagine :).
For me at least, I think the Steam Deck has it beat these days, although I'll admit I miss the smaller form factor sometimes.
There's a cottage industry of retro emulation machines that all have much better battery life, more faithful control schemes, etc.
The Steam Deck shines because of all the other things it can do, but those mostly come at a cost to how great of a retro emulation handheld it is.
I have it in my pocket all the time and put has save states, fast forward and low power standby with instant power on.
I can play it in short busts whenever I have a few minutes spare instead of using my phone.
I recently beat Pokémon Emerald for the first time thanks to this and I'm further through dk county than I've ever been
Btw that is 6 years ago or starting 7. No need of any update?
If so, I'd recommend EmuDeck . It took me about 10 minutes to set up and has emulators for essentially every platform you could want. (Just need to have roms.) Also, it's open source .
 - https://www.emudeck.com
 - https://github.com/dragoonDorise/EmuDeck
Is it true that 3DS hardware supports Genesis games (as seen in the screenshot)? I'd love to know the story there. Was Sega involved? How does it works in hardware, since the Genesis has 68k/Z80 CPUs, and the DS family uses ARMs?
The GBATEK specification  mentioned several times in the guide (not limited to the GBA, it also covers Nintendo DS, DSi and 3DS) feels like a real treasure trove of technical data.
: https://psx-spx.consoledev.net/ https://gbdev.io/pandocs/
This will be a document I'll keep around for the foreseeable future. Amazing work.
Granted, the saves are binary blobs but once you find the value you want you can find an entire struct of data along side it. There are tools like imHex which help the process and help you define the structure of the save file. It's become a common project of mine to save hack and then build a save editor when I'm confident my changes work.
Asking because I don’t actually know, I’m just recalling a lot of my early ROM hacking, and indeed discoveries in ROMs, by manipulating memory and savestate rather than the ROM itself.
To hack a ROM you need to know how to decompress the data, and then recompress your changes. A given game might use multiple compression formats.
In a general sense, I suspect the latter is more popular because it's not illegal to modify/distribute save state data; ROMs certainly can be.
Obviously, if you want all 151 Pokemon captured, you would do that through a save state. But if you want increased chances of capturing Pidgey, it would certainly be easier to distribute a ROM (or delte, in this case) with those new ratios baked in.
I used to do game save file hacking on palmOS as a teen. Was a hoot. Eventually turned to full blown “cracking” of software. That was a fun hobby.
The info isn't embedded on the page, but the download button for the PDF is unforced but available
Edit: Looks like this thread has the info from the PDF embedded:
Open to hear any good suggestions for PDF hosting.