Hi,
I reply to the questions one by one:
1.- The commands look correct. However, the interpretation may be slightly different as now you are not calculating the mean, you calculate the weighted mean. See the full explanation here.
2.- My understanding is the first option, that it is sampled at every “step” of the streamline. I imagine that the usage of ACT + sampling only at the ends will give, for example, very low values in the FA-weighted connectome. But I don’t know for sure the answer.
I hope this helps.
Best regards,
Manuel