No, they're both just boxes. Don't get hung up on roles defined by books.
Spacers are a fiddly old-school frame-spacing solution, and more plastic the world doesn't need. Castellations are fine, but I found they ripped nitrile gloves and the frames swing about. When I was at your stage I worked them down from 11 to 9 slots and was getting 4 & half lbs on many of the frames; I thought I'd found the answer!
At the same time I also had Hoffmans, but then discovered Manleys. One year the SBI came round on a routine check and said with good humour
I don't think you know what your'e doing, Eric. She was quite right, so after a ponder, I junked the castellations and Hoffmans, went over to Manleys entirely and have been happy ever since.
Don't bother.
That combo is a tentative attempt to respond to the need for more brood space, but frame management is limited (you can move frames between boxes only one way) and the extra space will not be enough for a good queen.
Another negative is that B+half is the work of two brood boxes but the benefit of only 1+half, so go double brood and be done with it. By comparison, many of mine are on three broods and a couple of supers by late May, and it's that extra space for both laying and storing that reduces swarming.
No, not at all; they show that you're thinking through decisions and deciding your own course, which is to be applauded.