Good to see you doing a ton of research. I went down the same path. Eric Cortina, Scott Satterlee, Pan handle precision on YouTube, Snipers hide, ultimate reloader, and many others. You need to inform yourself (doing a great job so far) and you will make your own methods. I will say I try to go with the most popular stuff.
There are guys who have vetted out what works best and there's no sense in trying to reinvent the wheel. For instance most guys run h4350 in 6.5cm, Varget for .308, and H1000 for 300wm. There are several options for powders but those are the most popular and I can see others testing and save time and money working up a load.
On the other hand I have seen people get crazy with stuff like primer seating. I have a K&M seater but just use my forster coax to seat primers now. Guys say you get more consistent SDs with better priming methods. I tried a few things and found that if I uniform the primer pockets and debur the flash holes I get low single digit SDs just using the Forster.
Lastly I found you can get great results with a basic setup. Most of the fancy tools just make it faster and easier to get good consistent results. Time is hard to come by so I invested in some of those tools to be faster and more efficient.
We are also lucky to have guys like
@Aeon and
@NBK here to help with their experience.