I've got two Xbox 360 controllers, [one still unused and vac packed since 2007- pretty much the last time the Xbox360 elite was turned on ] and a PS4 controller I bought to use with the PSTV unit I use for playing Pure & Pulse.

Who has experience using the DS4 software that allows the PS4 controller to work like a Xbox 360 controller wirelessly?
Are there any quirks I should be wary of?

Can I get a previously unused Xbox 360 controller to work wirelessly, or does it need to be wired up?

I don't know, I've purposely avoided this dilemma of mismatching software/components with PC gaming for years, by choosing to play video games on consoles.
The last thing you need is hardware problems, let alone video driver problems.