Best way to install bootcamp and partitioning question.

the bootcamp assistant will shrink the OSX partition without hurting it. It will make a BOOTCAMP partition for you and also let you download the drivers before installing Windows.

I cant say for an 8.1 install, but I did mine again last week with Win8 then updated it via windows app store and all is well

 

I used these steps in the link below to install Windows 8.1 on two macbook pros. When I tried doing it the normal way I got errors. Let me know how it works out if you decide to try it.


https://discussions.apple.com/message/23545484#23545484#23545484

 

The diskutil in OSX knows how to resize a partition. As long as there is enough space you can resize partitions any way you like.
Usually you cannot move the starting place of a partition so once you split up the ssd you should be certain about the size. You'd have to backup and restore the ntfs windows partition each time you'd want to make it bigger. Since the OSX partition starts at the beginning anyway you can in theory resize it all day long and make room for as many more partition as there is room for.