Keep or trim the "popcorn" buds?

Personally, yes I’m taking off a lot of those lower bud sites. And yes I would do it all at once.

Everything under the net should go. As you say, the buds and leaves don't get any light and just "waste" the energy of the plant.

yo quitaría los que son muy pequeños y apenas no tienen pistilos, el resto los dejaría, algunos tienen buena pinta

I would go all at once. I have read stuff that refers to lollipopping as LST and I have to admit the impact is about the same as bending the plant a bit or moving its lights. I want to stress take all of the small stuff. Small buds gotta go. A small top between two big ones - get rid of the small one and the big ones will fill that space. Make room for your main cola's/topps to grow and anything else is a waste. My preference is to try and do it all in one shot. But leave some of the fan leaves on the main tops. So as not to hurt the plant too much at once. Then come back and take them later as they are useless.. Clear as mud?