Flat, A weighted, or C weighted RTA measurments?

While I'm waiting for ADS to get my Maestro to work right I figured I would tinker around and try to smooth out the FR using the factory speakers.

The Alpine X008U has a 9 band PEQ and I've got a Phonic PAA2 for measuring. I've already adjusted TA (for driver's seat).

Question is the PAA2 has the option for RTA measuring: Flat, A Weighted, or C Weighted. Which setting should I use when taking measurements?

Also should I just use pink noise and take snap shots or 20-20khz sweeps using peak hold function?

Flat