Hi @OverripeSteam86, welcome to the forums. As for where to buy, this post sums up the 2 main options (MS Store or Steam), and is well worth reading. There are no drawbacks like you mentioned regarding either option. I went with the MS store, and would recommend that if you have any interest in XBOX Play Anywhere, etc.
As far as hardware, you cannot control the airplane using the mouse. You can get by for a short time using the keyboard numpad and autopilot to fly around, but you will quickly want to pickup a joystick. You can also get an xBox controller and use with Windows if you like. Expanding from there really depends on your budget and preferences. The Honeycomb brand of yoke / throttle is very popular.
What are your computer specs (CPU / GPU / RAM)?