Niv-Mizzet Reborn reveals the top ten cards and puts one card of each color pair (exactly two colors) into your hand, so it draws as many cards as there are distinct guilds in the reveal
There are also several categories of events which dont use the stack, and thus do not create a window for any player to react before their effect takes place
While you can use basically any card as your commander still (except for a few choice powerhouses), some are going to be a bit more fun than others
Also, you may want to consider either Ghostly Dancers to be able to reuse your exiling enchantments or Rest in Peace to shut down your opponents' graveyard interactions
You'll be among the first to know about exclusives, announcements, and events.
When Chandra's Firemaw enters the battlefield, you may search your library and/or graveyard for a card named Chandra, Flame's Catalyst, reveal it, and put it into your hand