I see, so the switch is still limited in this.Two things:
Doesn't matter; homebrew I/O speeds aren't great, and you're loading about 400mb worth of assets on top of the game and engine.
The 'stuttering' is generating texture cache; that's why your frame times are improved as it goes on.
I've already commented on this as a request, and no, you can't load anything other than Duke Nukem 3D Vanilla/Plutonium/Atomic; No .GRP mods, no official addons.
Yeah it is actually more like 1GB with the music included.
Nothing much you can do about the "stuttering" I suppose?