1. You can undo delegation from the wallet in peakd.

2. Depends. If you don't have much Hive Power, I suggest keeping it and using it to reward the people and content you like. In fact, I recommend everyone to keep at least most of their power to do this.

I have about 200,000 power, I delegate 10k to Leo.voter, 10k to @ocdb. These have a return. The other 10k I donate to a charity account to help them build. Other than that, I keep everything actively under my control. Your vote is your voice, many people are selling theirs for what they think is profit, but losing in other areas because of it.