Hi my dual board is really only my mains in garage circuits as didn’t want another board and change over stuff the house has it’s own 20 way board.
This is just for illustration purposes please get a trained electrician to complete such work. Some of the stuff has changed like the main head 100amp fuse is protected by time delay RCD 100amp because the TT earth.
The bus bar is only used to switch the gen and mains to the output. I have used link connectors in the CU yep didn’t know you could get them either until the manufacturer of the CU had them listed 120amp link connectors
The AC in to the inverter is 50amps output is 63amps yes I have breakers on both in and out.
16mm2 has been the case before but you will not get a DNO upgrading you to 100amp main head without changing the tails to 25mm2 I’ve just adopted the same playbook which I try to do for every cable plus if the system changes/upgrades I don’t really want to strip it all out and do it again, once and done.