I believe there's some misunderstanding and
@b166ar's "suspended" status has nothing to worry about.
Meanwhile I'm glad I can answer at least one of your questions, since I was digging dualboot system topic for a long time before I made it.
I'm not completely sure whether rear m.2 supports SATA(In my case both ssds are m.2), but I have another 2.5" SATA disk plugged and using it as a backup disk for hackintosh (same as
@b166ar).
Speaking about Windows10/Mojave dualboot:
First I installed Windows 10(but order doesn't really matters), then unplugged m.2 disk with it, plugged another m.2 ssd into second slot and installed Mojave, after everything was tweaked, I plugged Win10 m.2 ssd back, Clover automatically sees it.
People here on forum and from ****** advice no to install any of OS while disk with the second one is plugged in, in an order not to mess up with the booting files, so yeah I did it this way, and have perfectly working system.