RF detector

You would have to read the detector datasheets to be sure.  A power detector can detect instantaneous peak power, peak RMS power or average RMS power.   The differences, aside from the instantaneous peak (or peak voltage) would be in the time constants and the linearity range of the the detector.

What kind of detector you use is very dependent on the amount of headroom you want your PA to have and what kind of signal you are amplifying.  If you run the PA very close to maximum power you will need a fast gain control loop to make sure the PA is not overloaded.  If you keep 6-12dB of headroom then you can use an RMS detector and have a longer time constant in your loop.  A single FM or continuous wave signal will have different requirements than a QAM, or multi channel signal that has a very large crest factor (peak to average ratio = crest factor). 

Are you using digital pre distortion?  This will allow more average output power without distortion products.

Have you looked into crest factor reduction?  This will allow more average output power without signal cresting causing PA overload? 

The LMV228 or LMV232 datasheets may have useful information.