Hi Bro, 10 medium fishes.....think you going to tangs or big angels? For tang, in general, they might not need chiller. For angels, some do need. Please study their requirement before commiting.
Coming to your question in changing water, for a start, it is definitely recommended to ensure good water quality for your fishes. However, as your tank matured, this routine MAY cut down. However, you have make the judgement. There are reefers who dont change water for a year and their fishes still doing fine while others didnt change regularly, the tank crashed. As for the topping of water for vapourized water, yes, you must to ensure the sg level is constant. Lastly, frequency in changing water can cut down once your tank matured but there is definitely risk factor you have you take. I may be wrong, open for correction. Hope this clarifies.