"In Allied Commanders, you play as one of the many heroic leaders in the StarCraft II universe. Each with an arsenal of various powers and abilities and a select group of unit types which you may use to compose your army. All of these tools make playing each commander a unique experience."
You should check the link below to see what each races commanders do and which one you might like with your play style.
http://us.battle.net//sc2/en/blog/19829510
Adding another multiplayer mode to Starcraft II sounds great and I am seriously looking to check this out. So far there is no release date for Legacy of the Void I know of but when one is known, i'll let you know.
You can pre-order the digital Legacy of the Void version now and if you do you get access to 3 prologue missions. PC Gamer recently reviewed them and if you are interested in learning if they are fun, check out the review below. I haven't played them yet as I am going to get the physical collectors edition and it's not yet available for pre-order.
http://www.pcgamer.com/how-starcraft-2-legacy-of-the-voids-prologue-missions-set-the-stage-for-the-finale/
