I'm guessing: what if the 21 BPs collude and don't include your transaction?
The BPs are voted in by the EOS holders. So if the BPs are not behaving appropriately then the EOS community simply votes them out and a new BP is voted in.
Yes. 1 coin = 1 vote There is a couple “sister chains” Telos and Worbli that are developing a slightly different voting model that are expected to prevent whale manipulation.