Hi Jarek
The engine battery is a 42Ah lead AGM one which is connected directly to the alternator and therefore is always being charged when the engine is running. The Victron dc-dc charger is connected to the engine battery and charges the 200Ah LiFePO4 battery only when the engine battery reaches a preset voltage. So the engine battery is always charged first. As far as I am aware it does not support solar panels. You will need a separate controller for that. The Victron website has a good diagram showing how the circuits are wired up.
The other issue to be aware of is to fit a high quality fuse to the LiPo battery. I was under the impression that a fuse was a fuse but apparently not so. A class-T fuse is the gold standard but these are quite hard to find in the UK.
Best wishes
Andrew
Ps. Sorry about the name mix up.