Yes they are fully compatible. Both Angelfish and silver dollars are community fish and will be fine living together in a general community tank. Remember that silver dollars get large.
If you are planning to get a Silver Dollar as companion to your Angelfish, you can do so as they are compatible. There is no harm in putting them together in one aquarium!
Yes they are compatible when you have ample hiding places such as plants and decorations. This wil allow the angle fish to have a safe place to hide if the silver dollars get angry.
