draw is easy - i thing maybe there is alredy some component what i can use for it..
where i can change curve with some "vertexes" / add new ...
same for "graph" i see there is some "magic" in AudioProcessorGraph but i dont know is posible to crate some custom graphTree.. or something like that.. just to work with it, by draging nodes, and make sore that all joints left as is, and some common way how to serialize that data.
just dont wont "investigate bicicle" (something that already is done)
There is no special component for drawing envelopes and curves. You'll have to roll your own. I have to again refer you to the demo host that comes with JUCE with regards to your second question.
btw - about curve - for me it sounds nothing hard to imploment - but it would be nice (if i be not so lazy ill create pull-request) if that component be there