The Coway Airmega 400S is very quiet in our house. When the air quality sensor detects good air quality, you won't notice it working even when sitting right next to it. As the air quality degrades, it steps up the fan speed to move more air, and the sound is a pleasant white noise. External appearance is modern, and though it does take up some floor space, it is intended to be used in larger areas so that shouldn't be a factor. The app for your phone has room for improvement in both the notification and reporting areas, but it is usable. And the scheduling feature allows you to set up times with particular configuration settings -- we use it to have it turn off during our sleep times.
This Wi-Fi version, the Coway Airmega 400s not only, is not only very effective at air purification on the highest setting, it covers a large area and it is super convenient with the Wi-Fi settings to control it via phone and/or remotely. I highly recommend it. It is recommended by some top air quality professionals. Especially if you can get a good price on it.