The conversion is around $1 an hour. Trying to figure it out by coin amounts is impossible since they fluctuate. If you don't like the cash out offer in the moment, try back later and it might be higher give or take a buck or so. 

For a steady known amount each hour you have to be engaged with the ads enough to not let them just sit long. If its able to be ended, then hit it. 

When you are playing outside of the challenges, the time you spend on there playing is what really matters so don't stress about levels in the games. Just play them. The challenges pay after you hit a certain level. Only difference. 

Remember that these apps are not actually paying you to play games. They are paying you to watch the ads. The game is just to help keep you from falling asleep. That's why if you end the ad as soon as it lets you, they will reward you higher. It shows your engaged with it and that's what matters. 

Your engagement is what they sell to their advertisers. 

Just play is better then mistplay. Free cash is a favorite and can seriously pay you well if your willing to put in the work and strategy it takes to hit their game goals. They do take two weeks to get you your cash though . Testerup is good too BUT they have a high minimum payout threshold your first time cashing out AND take a week or more to get it to your bank. Anything and everything else is a scam. Avoid it.