It's just foundational knowledge to know where you operate within the whole. If "edge" is defined as the factor that allows a person to take better actions than the counterparties on the other side, then it is quite reasonable for people to want to know whether or not the place they operate from provides an edge and, if it does, where it may lie vis-a-vis other classes of participants.
In relation to the large capital pools, the private trader operates in a parasitic role. I used a reference to the go-go tech days when scalping on Level II involved watching the larger players and knowing whether they were a buyer or a seller. Of course they were always on both sides and they could also hide behind INCA, but on many days their operations were obvious, and when the largest players were on the same side you took a trade in anticipation of being pushed by them. In other words, you took some of the liquidity they were going to need. That was the edge.
Now, if you're some kind of yo-yo, you see the words "scalp" and "Level II" and automatically assume that I'm saying that the edge is to go for eighths and sixteenths. Anyone who thinks that going for eighths and sixteenths was an edge that ever worked was a SOES bandit. Not everyone who traded on Level II was lucky enough to be trading at that time and I don't think that era lasted that long. The focus when I traded was on staying in the trade and pulling out sticks and not jumping off just because it's a tick in my favor. The important point is, the goal was front running the larger players. For trading index futures, it takes a bit more sophistication to do this but I see my place within the whole as pretty much the same.
Regarding your list, I think it covers all the bases. I can't cheat even if I wanted to and being too smart doesn't pay. I would just change the last item to, "Be ahead of others." Being first feels good, but trying to nail that extreme tick on a turn can get costly.
By "externals" I mean all the things outside the trader that are required to exploit the edge - a quiet place, furniture, equipment, software, trading account, etc. These are necessary but easy to gather.
Thanks for asking.