Board Software
ASUS is in the process of transitioning to new layouts and features with Armoury Crate, which is its one-stop shop for most software features, including fan control. We got it working eventually but only after half a day of messing around, and not without lots of failed updates and things not working. In the end it seemed to resolve itself with Windows re-installs multiple times, with the software itself not seeming to fix things and the software not wanting to connect to the update servers, which you're forced to do before running features such as Fan Xpert. ASUS is looking into these issues, but they did eventually resolve themselves, at least with our setup.
As we've mentioned previously, the need to download obscure feature libraries in order to access basic functions such as fan and RGB control is going to confuse a lot of people, and it would be better to adopt the approach MSI has recently used and just allow you to download specific items. Fan Xpert is particularly useful as you have nearly all the options you do in the EFI from the comfort of Windows, which of course allows you to configure your fans while doing tasks you actually perform.
As well as the usual RGB software for controlling the onboard headers, the ASUS ROG Crosshair X870E Extreme has options for controlling the LCD too. This can show graphics, your own image, or a variety of hardware monitoring displays with configurable readouts such as CPU and GPU temp, fan speeds or voltages.