Regarding Payment Screen Settings improvements I added few improvements.
Currency Setup
On payment screen settings you can define a currency separated by : character.
When a currency is defined amounts will appear with a currency symbol and changing currency will also change button’s currency symbol.
Automatic Buttons
You can add * symbol in front of an amount and it will display Payment Due amount rounded upper to the button amount.
On this sample first button will round up payment due amount by 1.
You can try different setups. For example keep 1 and round 5 button.
In this case second button will display rounded amounts. If multiple buttons displays same amount one of them will remove.
On this setup buttons will keep their position.
Multiple Automatic Buttons
You may have multiple Buttons. When multiple values are used buttons will get sorted by their value.
We’ll have a lot of buttons now 
