Why use a third party gauges / radio software?

Newbie here. In the flight sim planning stages.

I have the beginnings of a decent flight sim.
Quad server / FSX / High end video card / don't know how to find out the frame rate but it is smooth, even with two 3rd party gauge demo programs running and several flight sim window views open.

I'd like to go with touch screen monitors to enable me to not have to "hardware configure" to a specific model. My first will be a C172, and I think with the touchscreen approach, I can switch back and forth between conventional gauges and glass cockpit with just a software switch.

I've seen PM and Peix software and vasFMC, etc. Ran them all at the same time with multiple FSX windows and everything runs really smooth with FSUICP. ....but....

What are peoples' experiences with the touch screen approach?

Will the triplehead2go work for what I have envisioned or would it be more practical to use a multiple video card approach?

Why do I need a third party gauge/radio software?

Can't I use FSX for it all? Using triplehead2go, main view to projector, undock gauges to a 2nd remote touch screen, and the radio stack to a 3rd touch screen?

Help is appreciated.

Don't know the answers to all of your questions, but shift +z will toggle through several onscreen displays of flight info: including framerate.