Two questions about creating particles on particles

Hello, how are you doing during the cold winter?

I’m trying to make forest scene, and the first step of making tree was just fine.
But soon I’ve stuck in the process that planting the trees to ground plane with particle system.
In short, I tried to make particles, with the object that already have particles.

Watching the simple image I made may help you to understand the issue quick:

Should I just convert the twig particles into mesh and join all to single object?
Or are there more better, smarter ways that can manage the small particles?
(Because if I convert them to mesh, it takes too much time to edit the twigs that on the trunk indivisually)

The following question maybe can have a sense only when the first problem solved.
Here’s an example image:

As you see, I’m wondering, if I find a way to show the particles under particles, can I give different(randomized) seed number to them?
Because it can give the trees more variety shapes(and so do to forest) if it possible.