I'm quickly realizing that additional lighting (IR or white) is a necessity for my situation.

With that said, what is the best approach to wiring for low voltage? Is it better to have one large Power supply centrally located and distribute from there? Or should I run individual power supplies for each relative area?

My main concern with a central PS is the voltage loss over the ~100-150' between point A and B on opposite sides of the house (or so I've read). On the other hand, individual PS wouldn't be fun either.  This will all be in the attic, so hardwiring and enclosure is a must.

As far as IR Illum:  Are there are sources out there that determine throw/spread of all the various options? Or should I just buy a handful and see what works?

One central power supply is the route to go, it makes trouble shooting a lot  easier.

This is true.    What is your worry about voltage drop?  Make sure your power conductors are sized for the load.

I wouldn't place it in a attic, the heat during the summer months will fry the PS. A simple wall fish is easy.

A simple wall fish, yes. A fish through fire blocks in this old house, not so much!

I suppose I could put it in the network closet...

look for a "CCTV" power supply that supports your required voltage and has individually fused outputs.   Then home run to each device