vertical spacing between staves in lead sheet

I created my first music sheet with MuseScore and I like what I am seeing. I tried to work with Lilypond but as powerful as it is, way too complex for simple stuff.

Anyway, the only thing that's bothering me is the vertical space between staves. And in order to deal with this, I found that only two settings in Page style helps for me: System distance and V-frame staff dist.

When I adjust System distance, it looks like it's going to work but then the changes aren't consistent. I have two pages and the first page would have smaller spacing but the second page would have more, etc. I just don't get the behavior. Perhaps it's trying to fill up the second page and so increasing the spacing to compensate? Not sure and how I'd work around that either.

V-frame staff dist also seems to work, but I can't quite make out what it's doing either. It matches up after certain amount of spacing (like after 5.0 or something).

What is the difference between these two settings and how do I get my staves to have equal vertical spacing in all my pages?

Thanks