Go the Topeak website (google it). You will find plenty of rack options, but better yet their racktop bags give you a few additional options, including one with a fold-out pannier on each side. The mini-panniers are just that -- mini -- and while I have seen them on other bikes, I am not sure of their longevity. But they may suit both your commute and light touring aspirations. I have several Topeak racktop bags, including one that is around six years old, and still like new despite a lot of use. Their most significant advantage is that they lock on to the Topeak rack with a slide system, making them very secure for all types of riding, including MTBing.

Otherwise, get a full rack, set it up so that it is level or very slightly tilted forward. If your chainstays are nice and long, I would suggest (but not guarantee) you should have no troubles with heelstrike on panniers, even the larger ones. jamawani's suggestion about the panniers moving forward might apply, but I have found the panniers usually take care of themselves if they are cinched down tightly with the inner strap.

You do need to be careful about mounting the panniers as far back on the rack as seemingly possible, as this can upset the handling of the bike both in corners and while standing to climb, especially as you seem to have a large frame. The centre-of-gravity weight of the panniers should be ahead of the rear axle.

Might sound a bit technical, but I have a 58cm steel frame and load positioning on the rack can have a quite dramatic effect on how the bike handles, especially when climbing while standing.

Finally, make sure you use the spring washers when bolting the rack on. Either that or a drop of Loctite 242/243... lost bolts are common, and while not fatal, a damned nuisance.