Just to keep banging on saying Portal killed lots of RAF crew for dogmatic reasons does not work for me.
Oh, the more I study history the more important it seems (to me at least) to understand the people behind the decisions. The 'why', to explain the 'what'.
And that means you have to examine their motivations, attitudes, ideas and ideologies.
This is commonplace in some areas. You can't separate BC's campaign without examining Harris for example.
But Portal doesn't get nearly as much attention as he should. He was at the heart of a lot of the major decisions the RAF made (or backed his subordinates when they made their ones), but since he was the boss he had the responsibility.
Right from the beginning and the appalling way Dowding and Park were treated after the BoB, the 'leaning towards the enemy', the debacle of Coastal Command, Malta, NA, et al. He was at the heart of all the major decisions made. Therefore has to take at least some responsibility.
Plus he had his particular personal prejudices, of which his antipathy towards the LR fighter was just one and that, naturally, affected his decision making and thus tactics, strategy and even personnel selection for the RAF throughout the war.
Therefore you can't select out 'what' the RAF did throughout the war, without looking at the 'who' and the 'why'.
One way of looking at it would by doing a 'thought experiment' and imagine that (say) Portal had been really for a LR fighter and pushed it real hard. What would have happened then? What could have been done and how would that have affected strategy and tactics?
I pick on the LR fighter issue more than some others, because it was a critical variable in virtually every area of air strategy. The lack of it meant all sorts of limitations on what could and couldn't be be done . To take the obvious dependency, no LR fighter, therefore bombers have to fly at night, which means they can't (initially) hit anything, therefore centers of cities is just about all they can (sort of) manage to hit (sometimes) and you need heaps of them to achieve anything. Each of the decisions, post the LR fighter one, is made for you therefore that is the critical one to make.