Can delegate when powering down? Yes No
I think this doesn't apply to new SP awarded since starting the powerdown, as the powerdown calculation is based on the total at the time. So if you are powering down, throw on a few thousand SP, this extra can be delegated. Also, I'm not certain, but I think you can set how much of your SP you are powering down, I could be wrong about that.
"Delay between votes" is kinda irrelevant in this because the delegated SP is de facto the possession of the curator.
Yes, it's important to note that delegating SP benefits the SP of the curator, not the delegator. Also, with Streemian, the operator gets their own (should be larger) share of the curation rewards and followers progressively get less the later the bot puts their vote on.
Yes, I worded it wrongly. Hopefully it's clearer now.