I, of course, don't mean stealing or copying the weapons and art; I mean how the controls for the guns and melee work. The game's style is so streamlined, and I think it's great!
In standard FPS', your weapon is always at the ready, and you have a separate button for melee, if you even have that.
I would like to know how to keep a gun lowered, have M1 be melee; M2 be shooting from the hip, and holding shift and M2 is aiming down the sights, like in Hunt: Showdown—does anyone know how to mirror that?

This can all be done via animation contexts and some careful coding in C++.
It all depends on the implementation of your weapon system on how your melee works (through physical collision - hard to pull off right, or through simple short distance ray hit - much easier).

You will need to get into C++ to change this though, especially in the GameSDK.

Thanks! I've been dying to know, and now I have a step in the right direction. Now I either need to get better at C++ or find someone who is.
I'm very grateful.

No problem, you could probably implement a prototype using the RayCast node in Flow Graph. But you will still want to create a "Dummy Weapon" and some additional animation poses etc for holding the melee weapon. You may still need a little C++ to override/remove existing weapon mechanics unless you use a custom model as explained in our recently released animation tutorial videos:
https://www.youtube.com/watch?v=xP1NpW_iT_A
https://www.youtube.com/watch?v=kqZubpCYdAM