[amsat-bb] Newbie Question on AO-51

I am a relatively new Tech learning to work the LEOs, and have a question specific to AO-51. On AO-51's status page at AmSat.org, it lists a Mode V/U (J) "QRP" frequency with no PL tone, and a Mode V/U (J) frequency with a PL tone of 67.0 Hz.

What's considered the maximum wattage to operate on QRP? Also, since I've never operated on the "PL" frequency, is it even active? Do "non-QRPers" use it, is it available?

Thanks for the help!