Power options cleanup

[ChaoticMind]

I ran through some inconsistencies when preparing my PR a couple weeks ago, thought I'd upstream them.

Basically, when run via the tests, show_power has types (bool or NoneType or str) that differ from when it's running through other means (str, set via the "choices" list). I noticed this when creating the -e parameter, and the type consistency was a source of confusion. I speculate that the original cause is simply a bad copy/paste from other parameters that actually are booleans.

This PR also removes the limit,draw option, as it's exactly equivalent to draw,limit. One may think it behaves differently (switches the order or something, which it doesn't). Best to have a canonical option instead, imo. Technically, draw,limit is also exactly equivalent to limit, so I suggest removing one of them as well.