BeagleBone Development, right choice? OS? GUI Tools?

I have an application that I want to see if the BeagleBone Black will handle.

The application needs to be able to provide an HDMI output. Provide a USB host interface to a mouse, a keyboard, and a virtual serial port via USB, and other interesting things such as DJ Consoles, etc… Provide a USB device port to slave to a USB host port on a PC providing the PC a virtual serial port communications path.
Needs to be able to provide a simple GUI with interfaces such as buttons, sliders, etc., and also a couple of graphical items that may act like meters or like oscilloscope type display, on the same HDMI output, in real time.

So I need some advice from current users.

New to BeagleBone and do not know how well the different operating systems run on it. How “real time” they are.

I would like to try to start out by using the standard Angstrom distribution, and add the code for the GUI and the USB interfaces.
Seems simple, but, not sure where to start.

Is Angstrom a fairly good fast easy to modify distribution?
e.g. how do I handle virtual serial ports, where do I find them, how do I add drivers?? Lots to learn, so any pointers in this arena, I’d appreciate.

Is it possible to build code for this on a Windows PC? Or should I do it all in Linux. Not sure of the possibilities there.

Does anyone know of any good GUI development tools that I can use to generate WOW GUIs with push buttons, sliders, and meters, and possibly even things that look like spectrum analyzer sweeps.

Appreciate any inputs any can give. This is going to be new to me, but a lot of fun.

Just wanted to make sure I am starting with something that can do what I want, see what tools others have used,