What Limits Scrivener 4 Formatting 4 Amazon & B&N ??

I have just started the Free Trial but wanting to know more, I visited the forum and found posts that seemed to indicate a universal feeling that you MUST have MS Word or something equivalent and export your work in order to final format, presumably for Amazon and B & N. I was hoping not to need MS Word, because of the cost. Now, of course, I can’t find the posts. I believe this question would be appropriate here.

I am just starting my final formatting, but have at least 2 and possibly 3 books to do. Any help would be greatly appreciated. I believe I will love Scrivener, butt don’t want to spend too much time, if it’s a dead end for some reason. The first 2 books I will be releasing are collections of short stories, but I do have a screenplay I am working on as well.

So far, I have noticed what may or may not be a limitation, unless it is my inexperience,… that is,… I want my line spacing to be 1.15 and in MS Word, you must indicate that, along with “multiple.” When I do that in Scrivener, it seems to accept that setting, but I see it has later changed on it’s own to 1.2 If that’s it, I’m good, but could someone remark on my concern?