1. I would never just sub any old primer out for any old primer. Of course I’d stick within same class. As in, large rifle, CCI 200, WLR, Fed 210, Rem 9.5... even then understanding that there are pressure differences so one should start low and move up with charge.

To points 3 and 4. I understand the differences in bullet construction can matter, but again, inconsistencies abound. Nosler gives the same reloading data for 120 gr e tip and 120 gr ballistic tip. Very differnent bullet, same powder charge is ok here though? Hodgdon language says not to mix lead free and lead data, as you stated too. but Nosler thinks it’s ok?

I don’t want to argue. I do understand your point. My point is that its not so simple. There is so much strange and seemingly conflicting data, inconsistencies, vintage issues, and component availability problems out there that it’s very tough to come to any confident conclusion and simply follow a recipe perfectly.