Touring - What Saddle Bag for Loaded Touring?

Is it common for people to just have the wedge or do people try to have something larger like a Carradice in addition to the panniers and loaded rack?

It depends on how heavy you travel and how you want to arrange things. YMMV, I think it's plenty to have a large wedge pack with a couple of tubes, a patch kit, a spoke wrench, and a small chain tool, and then pack any other tools that I don't use as much in other bags. You can leave that bag on full time, whereas you'd be tempted to swap a larger bag for a smaller one if you're just riding your bike around town.

Up to you. A handlebar bag is more traditional for touring; but I don't care for them
much. They do have their advantages, most have a plastic sleeve so you can see your map,
and you can reach in and get a snack without stopping.

No fan of handle bar bags myself, tho they are great for a map. Just don't need that much space for stuff I want to quickly access. A wedge or top tube bag (http://www.amazon.com/Sunlite-C-Sport-Bento-Bicycle-Frame/dp/B002E571XI/ref=wl_it_dp_o?ie=UTF8&coliid=I3K1G6D3LGPEBN&colid=159CDAF7PEMD2) is big enough for couple Snickers, cp, camera.

If you did some trimming to your packing list, you could get a larger saddlebag (Carradice LF Camper, for example) and consider just going with that and front panniers and ditching the rear panniers. I couldn't find the other threads that talked about this, but here are some pictures of what it might look like:
(borrowed from Path Less Pedaled (http://pathlesspedaled.com/))

http://farm3.static.flickr.com/2582/4100962286_193862e366.jpg

http://farm3.static.flickr.com/2751/4100208525_1a7cb7e2c1.jpg

http://farm3.static.flickr.com/2649/4100207741_00f76b1244.jpg

If we're talking about personal items, a handlebar bag or a wedge bag would work. Alternately, if you're not always going to be within arm's reach of the bike, a fanny pack might be in order.

The lesson being, you want your baggage to be modular, so that it's as easy as possible to access what you need at any given time, and so that you can easily offload stuff that you don't need. For me, "wedge pack" means basic tools that I always want to have with my bike. If I need space for warm clothing, I already have a rear rack on my bike, I'll just add a trunk bag. And if I'm going loaded, I'll put on the full ensemble, with trunk bag and panniers.

I don't use a saddle bag at all on my touring bike. I have plenty of room without it, and a saddle bag would get in the way of my tent. I keep my tubes and tools in a front pannier.

A handlebar bag comes in very handy for often-needed items, so you don't have to get off every time you need something. A Carradice bag is nice in addition to panniers or alone on shorter, lightweight trips. A rack trunk is also a good option. I wouldn't replace rear panniers with just the saddlebag. Smaller saddle pouches work nicely for toolkit, spare tube(s), etc., again on shorter trips.

Here's a full discussion of bike luggage and packing approaches (http://www.veloweb.ca/tourpages/bikebags.html).

I like the smallest wedge that will carry two tubes, a patch kit, and a few tools. I also like a handlebar bag, it is a place to put your map, allows quick access to your camera, and holds your valuables in one place so it is easy to take them with you when you go in a store or restaurant.

Trunk bags for most touring I don't get. They aren't especially easy to get to when riding and fit in the space where I carry the tent. That said I might consider one for credit card touring with 10 or so pounds of gear and clothing split between it and the handlebar bag. I especially might consider this if using my folding bike.

This is all personal preference though, so use what suits you.

I think a saddle bag in addition to panniers is overkill and will just encourage you to carry lots of useless heavy stuff. With a sensible gear list a large saddle bag like a Carradice Camper or Nelson Longflap can replace a couple of panniers. Also a saddle bag can get in the way if you want to strap stuff on top of your panniers

Here is a brief overview of some touring styles

http://wheelsofchance.org/2009/08/19/touring-taxonomy/

If you do choose to still run a wedge for the essentials, a suggestion:

run two. try the narrow, tubular tire style saddle bags.

This lets you shove whatever needs to get lashed to the top of the rack right down the middle underneath the saddle and the wedges can swing to the outside to allow the foam pad, tent poles, etc, to be strapped a bit further forward on the rack, as the wedge isn't blocking the middle of the space just ahead of the rack and below the saddle.

I really like having a saddle bag for the essentials... As in tube, patch kit and tire irons along with a multi tool... Pretty much the same stuff I have on my Roadie. Digging around in my panniers for the small stuff sucks. I tend to keep the big stuff in my panniers. I already have enough heavy stuff in my handlebar bag. Find what works and go with it.

One thing not mentioned is that it is kind of nice to carry the spare tube(s), patch kit, and a few tools in the same manner as you do for all your riding. For me that means the tiny wedge.

BTW, someone mentioned that they couldn't use one because they carry their tent on the rear rack. Since the little wedge doesn't stick out beyond the back of the saddle that is a non issue on my bike. The little wedge is just part of the bike to me and my bikes all have one that is there whether touring or doing any other type of riding.