What about other ad networks such as bitmedia.io and mellowads? I'm interested in trying out this ad network but I want to know how much can be earned based off user reviews.
Yes, but what is U-Ads payout compared to existing ad networks?
If you added the same code twice, tracking would be off as both the banners would show the same amount of clicks in your statistics as they use the same code.
If you want to track how many clicks each ad gets so you can play around with ad placement and see what works best, use two different ad codes.
Generally, people use two different ad codes.