Clownfish don't usually hide in caves and spend most of their time in the open areas of the tank. They don't really mind how the LR structure is assembled in the tank. Just make sure to make a good planting structure for the corals and some hiding places for the fish that appealing to you.
The answer to that depends on the particualr clowns, the female will decide where she is going to lay her eggs when the time comes. You can set-up a textbook nursery tank and the female will lay her eggs someplace else.
They usually lay their eggs towards the base of the anenome...my uncle breeds clownfish, rare, but he does, he's told me they often lay the eggs at the base of the anenome they host in.
Breeding is whole different ball game and in most cases it's easier said than done.
There is some really info out in the net about breeding clowns, but most likely you would need a breeder tank setup and do lots and lots of research to provide the clown the proper environment for breeding.