Are they customizable by now or will they be made customizable later?
The kickstarter demo which I've played didn't have the feature (or it's too well hidden for me to find it) but will the finished game have this, or is it already implemented?

They're already customisable.

Thanks for the info! Gonna wait and see if it pops up with the 10% during the sale again but now that I know that issue out of the way I'll be buying either way. :D

Related question.

Is the ship control such that using a joystick would make it better?

I started Startpoint Gemini, but am waiting until I have more space for a joystick, as that is a little clunky with a mouse/keyboard interface alone. Is this similar?