They look like 'Mysore' (aka 'Pisang Ceylon'). You can confirm this by observing if the undersides of newly unfurling leaves on the young shoots have a distinct reddish hue to them as seen in the photos posted below.
As for when to determine harvest maturity for a cultivar I am not familiar with, I always check closely every day and wait until the first finger or two start to turn yellow (indicating there will be no more size increase), and carefully observe how the fruit looks including: size, plumpness, roundness of edges, shade of green of the unripe fruits, and the state of the male bud. For future bunches, when the fruit is still all green, but appears otherwise the same as when you observed them start to turn yellow previously, then you should harvest. Ideally you don't want any fruit to ripen on the plant as they tend to go really fast from there and become targets for bird and mice and fall off when harvesting, but it's helpful to let a few ripen when you are getting to know your plants.
I've tried uploading photos of some mature/ready to harvest green 'Mysore' bunches for your reference but there seems to be an issue with the photo upload system at the moment so maybe I'll try later.