Freestyle / Lead - Does that just happen?

I think I fall into the category of ‘Intermediate’ I can bend all the holes but some of them are still only achievable briefly and so far there are only a couple I can go straight into without starting unbent.

My question is this. I am confident that if I follow JPs instruction and keep practising then I will get fluent and able to play all the exercises and copy other peoples riffs but I am not confident about making up my own. Is this something that naturally follows once you get comfortable with where all the notes are? I know people that only play rhythm guitar and can’t play lead guitar so does that apply to harp as well? Final question; do people playing complicated riffs just make it up as they go or is it more common to work something out in advance then play it like it is off the top of their head?

I think I have found an answer myself. I stumbled across a video by Jon Gindick that pretty much lays out the basics.

https://www.youtube.com/watch?v=P4zWSoib5BU

and there is a follow up video to further refine it (though obviously there is a lot more to learn to really nail it)