okay so here's the current breakdown of how 3D All-Stars works

I feel like I should preface that this is at current understanding and there may be more revelations

SM64 is heavily based on the Wii U emulator with NERD's own tweaks during porting

it still does vertex, code, texture replacements at runtime to up-res the retail Shindou rom for the Switch (yes, it is retail Shindou) https://twitter.com/LuigiBlood/status/1305806298953461761

Sunshine is fully emulated (with some DSP bugs, I saw?)

they chainload a separate nrolz which is just an LZ4-compressed nro with the actual emulator which is apparently like 25MB

that in turn does hash checks (and other stuff people are looking into to do game replacements) and boots the gcm

the gcm is the modified PAL rom (cuz NERD), with all language files, cutscenes re-encoded to black for the emulator to pick up on and replace, and recompiled dol

Galaxy is the really interesting (read: janky) one

the files for the game are extracted and endian-flipped, and the cpu code has been ported to run natively on the Switch's 32-bit compatibility mode

the Flipper GPU and DSP Audio are still emulated*, cuz they're a pain in the ass to port

*at current understanding

both Sunshine and Galaxy use NERD(?)'s newly developed hagi emulator, which also does file, texture, code replacements

interestingly there's no shaders like Lingcod (the Shield emu) to replace, all the up-res is handled in the emulator with their viewport patches (I'm guessing)

so if you're wondering why Super Mario 64 isn't 16:9 and the other games act weird, it's because it's a weird mess of emulation patches and porting to get all the advertised "features"

I can't comment on the remastered assets, ui/model textures and movies, but other people think the movies are just AI-upscaled because of some gross text artifacting and sloppy editing for button prompt audio