UE4 uses UDP for its replication, and is based on a client-server model. The physics simulation is also not deterministic.
I wouldn’t worry about those things, since UE4 already has most of the networking systems set up for you.
In any case, I would definitely have the server handle physics simulation and replicate movement of those objects to the clients.
And just decide whether or not you want physics to be simulated for these objects client-side as well.