Jumping in here to drop some Flex knowledge. Flex, in my opinion, is how to really take advantage of your controller. The main key to getting it to work for you is to get your zone settings as close to perfect as possible, which you have already done, so you are all set there.
Flex runs off of this idea of Managed Allowed Depletion (MAD). Easiest way to think about it is a gas tank. It watches each zones "gas tank" and once it reaches a certain level (this is defined by your MAD setting) it refills the tank to the top. This promotes deep root growth and creates drought tolerant plants, basically it's the correct way to water. It uses your zone settings to determine how much "gas" (moisture) your zones are using up each day, and it looks at past and future weather to see if there is precipitation that will help refill the tank. Each zone is handled independently, so if one is running low but all the others are fine, it is the only one that will be watered.
Flex does show future watering days, however it is important to note that these days can change with weather! If consistent watering days are necessary for you it probably isn't the best option. The duration for each zone will be the same every time it waters.
Warnings for when you first set up: In the beginning flex wants to make sure your tank is full, so it may seem like it overwaters right off the bat. Don't let it scare you! Also, the calendar can be misleading. It can say it is watering every day, but that is because zones can run independently of each other! Don't let that rain drop make you think you are watering your whole system that often. Last thing is durations may seem long, but this is because flex changes the way you water. Times should be longer but less often!