Well, now that you read it all and feel like you have it figured out let me ruin your day a bit. The white paper is hopelessly out of date. There is no interest being paid currently.

Holding SBD is fine if you want stability and steem power is good if you want it invested but DO NOT just hold liquid STEEM. It is devalued slightly every day by design. If you hold 1000 STEEM for one year and the price of STEEM does not change you would get less steem power for your STEEM a year from today than you would right now.