How does behave EXACTLY a PA ?

The PA on the modules is always on and cannot be bypassed (generally). The PA gain is ~20dBm which is 100mW increase in power.
So if the module has a maximum output of 1mW before the PA, the output at the PA is 100mW. since most module also have very low power modes, the minimum power could be as low as 150uW, but this is still going through the PA. Not all modules support the same low power ranges.

when Deviation says 150uW, it really means 'the minimum power supported by this module' when it says 100mW it means 'the maximum power recommended for this module'. 150mW is not a recommended setting as it is very power inefficient. You get less than 12% more range for up to 2x the battery drain. the mW value is not accurate in general (though we try to get as close as we can), and it represents antenna power (not battery consumption).

All of the PA in all modules are very close in total power output. they all have a gain of ~20dBm (which is the same as input mW * 100 = output mW), and a maximum power of ~150mW. However, the CYRF6936, A7105, CC2500, and NRF24L01 all have different power output capabilities. So if you have a NRF24L01 with a PA, it probably will behave exactly like any other NRF24L01 with a PA using the same antenna.