> Which is what I've done when installing Linux. Am I losing performance? Power efficiency? Features?

From what I read a year ago before doing this, you don't lose much, and software-based RAID (if you go for that sort of thing) in GNU/Linux is just as efficient/reliable, and maybe more so. And anyway, if you only have one HDD/SSD, there is no point in RAID.

> It also makes dual booting trickier if you don't plan it beforehand.

I don't think so: installing Windows will work just the same with Intel's RAID turned off.

It is simple enough to set up windows to use the normal boot rather than the RAID one. I've got my XPS set up with one drive in Linux, one in Windows - and boot into the drive I want to be in.