Problem with zentralized IPsec/OpenVPN mixed setup

[darkred]

Dear pfSense Communitiy
I am working with the following setup:

In the past I had just the two Sites B and C but now I have to add a Site A with a Omada TPLink Rôuter, over IPSec.
My problem is, that I am unsure how I have to configure the Phase 2 Setup, especially the "Networks" part.
As Local Network I would like to use nothing (I do not have an LAN, just one WAN interface), or the other to Networks 192.168.20.0/192.168.30.0. But that is not possible.
That do I have to do, that over IPSec I can connect to the Master-Firewall and Site B & C (also from Site B&C to A)?

Thank you for your supper,
Darkred