If a client (e.g. no. 7) connects to this server over L2TP/IPsec and has LAN address e.g. 192.168.20.10 like peer number 3, will the connection be successful or will it mess up with everything?

Each client comes from a dynamic public IP address, each public IP address has only one client, as expected each link has a unique local and remote address, each one is a separate peer with own credentials (policies, identities etc.) and there is no need to access other devices on clients’ LAN (only the MT through the remote address).

Bump.