First up some confusion. Generally speaking you'd use cardioid microphones in an ORTF
Read these articles:Stereo Miking Techniques
1 Stereo Miking Techniques 2
Here's schematic of it:
So if using ORTF use the cardioid
capsules on the NT5s.
If you're using the omni caps, then you'd need to use a
spaced array (or a Jecklin disk).
I'd opt for the spaced array.
and I'd generally record to two mono channels myself, but it's not a big issue as you
could always convert your stereo file to two monos if you had to.