Well, some minor scaling artifacts I could live with. I like a look that’s based on 2x internal resolution (no downsampling) for games that are mainly 3D, but that doesn’t go cleanly in 5x of course.
The cores mentioned do their own weird scaling things, e.g. the PCSX2 core seems to be fixed to 640x448. Not a problem for most NTSC games I suppose, but it’s likely suboptimal for the 512px stuff, not to mention PAL games, which why I’m only going for standalone and reshade now.