Don't N64 need an amplifier circuit because the RGB signals is weak?
Is there any noticeable difference using a RGB cable on SNES and Genesis and modding them both with this component board?
Is the pic quality is better using the component board compared to using the consoles' native RGB cable output?
Yeah, as far as I know, the N64's RGB does need to be amplified. The picture will be too dark if not amplified. there might be some models which do not need RGB amplification though, I'm not 100% sure about that.
I haven't done a side by side comparison but from what I've seen, I'd say that the component video quality with Turbokon's RGB to component PCB is as good as it gets. In the end, I believe that it all depends of what your setup is because the PCB will work only with a flat screen that has a component input that is 240p-compatible or a bulky CRT.
If you use an upscaler like the XRGB-3, I don't think there is any interest in converting the RGB signal to component before feeding it to the upscaler.