I have played it on my steam deck, I didn’t beat it because I got really bored with it (even after not playing it for 10 years, i still remember it so well…)…

honestly, it’s not the best experience on the steam deck. I get around 15-30 fps (30 fps in very tight areas, and down to 15-20 in the more open areas.) since it’s a stealth game 15fps isnt horrid… but it’s not a great experience.

audio will frequently cut out in the more intense areas (there were two parts in particular where the audio bassically couldnt be heard, but otherwise for me the audio was generally good with only occasional cutting out.), ppu/spu cache takes literal hours to build. you can turn off precompilation, but then every loading screen on your first time around will be actual minutes long. on top of that, one of the settings that almost completely stops the audio glitching is only usable once you have gotten past the intro (it causes a crash at the very beggining otherwise, meaning you will have to suffer through the intro, then save and restart the emulator).

but other than that… cutscenes do run great, at around 40-60 fps. and mgs4 IS mostly cutscenes. overall though, i wouldn’t reccomend it. I saw someone on youtube who overclocked their steam deck and it seemed to perform much better, but at that point you are drawing so much power out of the battery you are bassicaly married to the charger and… eh.

even without the overclocking, you are still gonna be pulling the full 25w out of the battery, so you aren’t gonna be playing this game as a on-the-go sort of deal at all, and the fans SPIIIN like holy fuck they spin. so loud. so fast.

something odd about op’s post is that uh… resolution scale bassicaly does nothing for me. I don’t know why it would, even. RPSC3 bassicaly chokes out the CPU and leaves the GPU clocked at like 200mhz the entire time. settings the resolution to 1080p only reduces my fps by like… 3. it’s a very minor tweak, and even when I set it to 480p it barely made a difference too, and its so much uglier you might as well leave it at 720p

all that being said though, despite the bad framerate i was still enjoying myself quite alot in the parts of the game that aren’t boring. mgs4 really tanks gameplay wise near the midway point sadly.

if you still want my settings despite this, I can hand them over in another comment lol