Personally I have found that using LED film softlights to be useful for scanning. I didn't have the time to do what this wonderful article does, which is research, design and build a decent softlight source.
In the old days, you might have been able to use a florescent 5600k light sources, as rated ones have a known spectrum that can be counted on. Having those in a light table would get you 90% of the way to a decent scan.
One thing I did note is that the second colour image appears to have nowhere near the aliasing or film noise of the first sample. Was its scanned at different settings?
I used a primitive setup: Flashlight mounted on camera and "guided" to the back of the negative, so not even remote flashlight because I didn't have that for the camera. I used Darktable for the conversion process and there were 3 key points: Exposing the negative to fully exploit the RAW channels of the camera, setting a proper black and white point in the conversion process, apply white balance as needed and maybe manually tune the green/magenta slider a bit. Usually, if all that went well, I received pretty clean results. If something got botched in the process, I would see the same noise as the top right image shows. As the article notes the resulting dynamic range is really low then, which makes noise pop out. Noise is also in the bottom right example image, but the larger resulting DR (and downscaling) hides it well enough.
In the old days, you might have been able to use a florescent 5600k light sources, as rated ones have a known spectrum that can be counted on. Having those in a light table would get you 90% of the way to a decent scan.
One thing I did note is that the second colour image appears to have nowhere near the aliasing or film noise of the first sample. Was its scanned at different settings?