So then, for SNES, NES, and I guess TurboGrafx emulation in RetroArch on Windows 10, my settings are:

Prerequisites:  Use 'Just Scan' or 'Screen Fit' on your monitor, and have your gpu perform "Aspect Ratio" scaling on the Display. Also, set your color temperature to Normal, if this option is available.

Drivers>Video>glcore

Video:
>Windowed Fullscreen Mode: Off
>Screen Resolution: 512x480
>Aspect Ratio: Custom
>Custom Aspect Ratio Y Pos.: -14
>Custom Aspect Ratio Width: 512
>Custom Aspect Ratio Height: 504
>Integer Scale: Off
>Hard GPU Sync: On
>Hard GPU Sync Frames: 0

Overlay:
>Overlay Preset: scanlines.cfg (under "wii")
>Overlay Opacity: 0.35
>Overlay Scale: 1.00

Shaders:
Shader #0: ddt-extended.slang
Shader #0 Filter: Don't care
Shader #0 Scale: Don't care
Shader #1: chroma.slang
Shader #1 Filter: Don't care
Shader #1 Scale: Don't care
Shader #2: ntsc-colors.slang
Shader #2 Filter: Don't care
Shader #2 Scale: Don't care
Shader #3: natural-vision.slang
Shader #3 Filter: Don't care
Shader #3 Scale: Don't care
Shader #4: aann.slang
Shader #4 Filter: **Nearest**
Shader #4 Scale: **Don't care**

(Set these all up and hit "Apply." Then...)

Shader Parameters:
Brighten Level: 2.00
Brighten Amount: 0.10
Contrast Amount: 0.00
Chroma Level: 2.00
I Amount: 0.10
Q Amount: 0.10
I Tilt: 0.48
Q Tilt: 0.52
I Tilt High: 0.52
Q Tilt High: 0.48
I Tilt Mid: 0.50
Q Tilt Mid: 0.49
I Tilt Low: 0.47
Q Tilt Low: 0.50
Luma Boost: 0.00
NTSC Intensity: 1.00
Natural Vision Gamma In: 2.65
Natural Vision Gamma Out: 2.20
Natural Vision Luminance: 0.96
Natural Vision Orange-Cyan: 1.20
Natural Vision Magenta-Green: 1.10
Interpolate in RGB: 1.00
8px Overscan Masking: 0.00
Force Bilinear Filtering: 0.00