Ark is actually a delegated proof of stake. You use your Ark to vote for a delegate and long as that delegate is in the top 51 they forge Ark then payout their stakeholders. Ark you probably want at least 1000. More you have the bigger the payout. My returns are still pretty small but I chose Ark because the payout seemed better then PIVX or NXT. Even with a smaller amount I'm at least getting something paid out every few days. With those two I'd be waiting forever even with 1000 PIVX or NXT to get payouts.