If you do, draw X cards, then you may put a permanent card with mana value X or less from your hand onto the battlefield, where X is the sacrificed creature's mana value
You probably didn't need me to tell you that
Kuja, Genome Sorcerer Kuja, Genome Sorcerer puts a Rakdos spin on what's usually a blue-themed archetype
This means you can hold up mana during an opponent's turn for removal, interaction, or whatever else they might throw your way
Attacking and blocking creatures remain such until the combat phase ends, or until they are removed from combat for any reason
If all you're trying to do is gain lots of life with this combo, either of those commanders would be a great start, but we're going to go a little deeper