That is not the way the S+ works. You either play credit or cash
1. Credit mode, all bills to credit all wins to credit. If you insert coins, it does not add credits, but only coins played. So if you have 50 credits and insert 3 coins (assuming you have a 3 coin game), the you will have 3 coins played, but your credits won't increase. If you win, pays go to credit.
2. Cash mode. You cannot have credits in this mode, all bills in and all wins pays out of hopper, unless it's over the limit, in which casei n goes into hand pay mode.
The credit limit is basically the top amount of credits that you accumulate, if your win would take you over this credit limit, it pays coins as long as the win does not exceed the hopper limit. For example, you have 1000 credit limit and you have 990 credits, you win a 20 credit combination, it will pay all 20 credits from hopper.
The hopper limit is the maximum number of coins the machine will pay in any one event, either a cash out, or a win. If you hopper limit is say 300, then anything that will dipense 300 or more coins, will go into a handpay mode.