So currently, we can create one scene for EEVEE or Cycles, one for rendering with LANPR and a third one to composite both renders.
Or we can create a GP object, add a Stroke modifier to it and tweak settings in LANPR panel to obtain GP strokes overlaying our scene directly in Viewport.
Both choices are far to be intuitive and both have their own limitations.
Compositing workflow is complex LANPR render does not automatically overlay EEVEE or Cycles render like Freestyle does. And there is no LANPR pass as Freestyle in 2.79.
There is no Freestyle pass in 2.8, too. So, trying to work with Freestyle in 2.8 is as complex as using LANPR.
Ideal workflow would be to have as many Freestyle, LANPR passes as linesets/layers created instead of being forced to create a copy of scene for each.
Creation of line style is limited to variation of thickness according a direction and choice of one color.
But we can create several layers and give a different linestyle to each one.
Generation of GP strokes is based on adding a modifier to GP object.
But to overlay geometry of scene, origin of this GP object have to stay at origin of world.
So, we can make more geometry variations through GP modifiers.
But currently, it looks like some modifiers are not well supported.
A Subdivide modifier does not affect all strokes of a simple cube.
And all generated GP strokes are on same layer, using same material (first one of material list).
xp8110 reported those problems. So, I would wait fixes of following week to play a little bit more with that.
What is announced may be sufficient to obtain something satisfying for people who want to combine LANPR renders and GP animations.