You set the maximum price you want to pay. We are using 2nd bid price. So you never pay more than the 2nd bidder. If you bid  $1, and the 2nd bid $0.75, you will pay $0.75.

Also like Tender says, we have a list inside of our publishers. Actually, this is RON, but you can block any sources you don't want to increase your ROI.

We have volume traffic, but If you want lead, signup etc, we recommend to add Productive targeting in your campaigns targets. Productive target will make your ads shown in only very trusted with leads historic. Price is higher with productive set has we have more advertisers in that category.