Because a field of the type long may only contain integer values, the most common way is to configure it as such - an integer. Additionally, you can add a validation expression (perhaps because the number should always be greater than zero) and a default value in the property configuration.
You can configure a long value as text, e.g. if you want to insert a placeholder text into the field.
Long.MAX_VALUE, no matter which input field type is selected.
You can use a long field for time scheduling, which is why you can select Scheduling as an input field type. However, this only works for a specific small set of properties. Therefore, you have to look for detailed information here.