Hello @aberger
1) What about the part number you use? You can find power mode transition time for your chip from data sheet, for example K32L2B3x:

2)"What is the impact on recovery time? "
->>
PSTOP1 is functionally similar to Stop mode, but offers faster wake-up at the expense of
higher power consumption. Another benefit is that it keeps all of the MCG clocks
enabled, which can be useful for some of the asynchronous peripherals that can remain
functional in Stop modes.
BR
Alice