For the AP power, Auto is good if your APs are getting background scans through. The AP will do a background scan, and then it can adjust your power according to the network environment at the time, which is ideal. Unfortunately background scans can be missed for various reasons, which means the AP wouldn't be adjusting the power to match the environment, and you might end up with an inappropriate power setting.
You can check if you're getting background scans through by running the command "show int wifi0" and "show int wifi1". You're looking for BGSCAN in the output and you want to compare how many scans are going through vs. how many were missed. Missing a few is fine, but missing the majority means the Auto power and channel settings are likely not a good fit for you.
For the client power (802.11h), unless you have clients that are broadcasting too much or too strongly, I'd leave that setting off and let the client devices manage their own power levels. If you do have to set the client transmission power level, it doesn't necessarily need to match the APs power level. Mostly you'll want to be sure you aren't forcing the clients to a power level that is too low, which would mean their signal may not reach the AP very well. With that in mind, I'd recommend starting high and lowering as needed, if you are going to try to control client power levels too.
