Question about transferring BMCA files to MacBook

Heya everyone, I hope you had a great weekend!

So, I have two questions - I have an iPhone 15 Pro Max, a M1 MacBook Pro and I just started using the Black Magic Camera App.

Question 1: If I tell the app to save videos within the app AND the photos library, won't that take up storage space twice as fast? It seems weird that I can't choose JUST the photo library. It wouldn't matter except for the situation that prompted my SECOND question, which is....

Question 2: If I go to transfer videos from my iPhone to my MacBook via USB (thunderbolt or whatever lol), my finder window shows my iPhone. When I click on it, I get a window different than I am used to (only been using Mac for about a year now). It seems to remind me of iTunes in a way. Anyway, when I go to the black magic section, and expand, I see the folder that has the media in it, but I can't get THAT to expand. The only way I could get the files to my MacBook was to drag the entire folder over - which is NOT what I wanted to do. Am I missing something? Is that truly the only way I can do this (I know about AirDrop, I don't want to use that for files this size).

Thanks in advance!