Worrying too much about structure can be deadly. William Goldman probably addressed the subject best, he said something like, "Find A structure." And that's about all I've read from him on that subject. Good advice. Don't let structure get into your head until you are sophisticated enough that allowing yourself to get that technical doesn't put out of the whole experience.
I look at it like this: There's a writer and a reader. The two have a contract. The reader will set aside his or her everyday life and read what the writer has to say ... but the writer has to make it worth their while. The exchange is about trading attention for entertainment or knowledge or both. Ultimately, structure is what the writer gives to the reader in order to convince them that what is coming IS going to be worth their while. That's the purpose. The fundamental. The strategy.
Believe it or not, unless you have been divorced from western culture your whole life, you probably already understand the tactics, the method of achieving a result good enough to get a first draft down. It's hard to apply much of what many of the books have to say until you do that.
Books on writing, especially books on screen writing (where doing it right is like doing great Haiku), go wild on structure. If you are a practiced writer who is in control of your medium it's all useful and can be used artfully. If you are not the advanced stuff will just slow you down and gum up your head with junk. It's worth knowing that people talk a lot about "three act structure" but there is NO RULE WHATSOEVER that you need to structure in three acts. It's just that you don't have a pattern until you hit the number three, so it's sort of the minimum: Introduction, development, resolution. "Development" can usually be about as many "acts" as you want ... until it gets dull or the least bit repetitious ... then you need fewer.
For beginning writers (for screen or literature) I like to recommend Linda Seger's "Making a Good Script Great." It gives just enough on each of the many subjects it covers to inform you and get you thinking, but not so much that it causes creative paralysis. It is also about REWRITING. As above, messing around with too much instruction before you have a draft down on paper in some form is a waste of time. The material in any writing "how to" book is just confusing until you have some work of your own to directly apply it to.
There is a lot of good books out there once you get going, each is got some quality ideas and some nonsense. I could go on about them all day but it's better if you spend your time writing.
P.S. I made myself type out several chapters out of a number of books I admired just to see how the writers were doing what they were doing on a word by word basis. I made myself type hunt and peck style to REALLY make it a technical experience. It really made me note how much or how little dialog they were writing, how long the paragraphs were, how deep into description they went and what their pace of information was like. It's a worthwhile exercise.