Took me a few days to make the time to look into it in detail.
It is indeed a "cheap board", $10 cc/cv variety, $6-ish now, certainly not high quality stuff. I am experimenting with digital control (which works well) to just play around - not anything serious to use but just to see what I think I know enough to make functional (is it so or not) and what I can learn from the exercise.
Finding the noise (which I knew but forgot), I connect up my other board (exact same board but unmodified) to get a base line to see if what I introduced made matters worst - yes slightly. The unmodified one show that same noise at perhaps 10-20% lower noise peaks. The trace below are made with an unmodified board.
The two attached photo are the noise (green trace on the posted pictures). The first picture is the "fast" shot (scope too slow to resolve the detail), the second photo is a zoom in by lowering the time/division. The noise frequency looks like it is around 100-200KHz.
Looking at the noise closely, I realize it may be the capacitor being drawn down, then for the rest of the switching cycle, it set at much lower level. I added a 1000uF output cap. It did a lot of good (say at 6V 100mA range), until the load increase to a point when the 1000uF got drawn down too. By about 1A, the trace collapsed into a clipped triangle. Just to validate, I upped the cap to a 4700uF, it delayed the start of the collapse to a higher current. Interestingly, when the power-draw is very high, the noise will go back down. I suppose it is at a point where the charge is insignificant - which lead me to think perhaps I should lower the caps on the board.
I am not looking for a magic bullet. I just like to hear some techniques so I can do more research into them, see how they work and see what I can learn.