Hello - I realize that your post is pretty old, but I just found it and wanted to reply in case you were still wanting some info on Toledo Bend lake.
I myself am not a sailor (yet). I do have a good bit of experience operating a powerboat on Toledo Bend; a 21 foot Xpress rescue boat with a 115HP Yamaha.
With regards to sailing, all I can say if from an observer's point of view. I've seen sailboats from Hobie Cats up to pocket cruisers (I'd say up to 26-ish feet), but they aren't very common.
In regards to water depths and winds, I can be a bit more helpful. Only a bit, mind, but I'll do my best.
Water depths are variable in the lake, but if you stick to the old river channel, you could sail a schooner through there. Overall depth gets better as you go south, of course. The north end of the lake still has a pretty bad issue with stumps, even in fairly deep water. It seems that the lake filled up faster than they thought it would when they built the dam, and the north end of the lake didn't have time to be properly deforested. So what you've got is not stumps at all, but old treetops that can snag a boat even in 30' of water - in places. Again, if you stick to the river channel (which is marked with buoys) you've got no worries. Water depth gets shallow pretty quickly around the shore and islands, because a good part of the shoreline has fallen/eroded into the lake in the 40ish years since it was built. It's mostly silt and sand, so if you run aground, you should be able to get off. If you can't get off under your own power, there should be enough passing sporting vessels who can pull you off, so you won't be aground for long.
Now for wind.
As you have no doubt seen on maps of the lake, the basic overall orientation of the lake is north-south. I only point out the obvious because its relationship to sailing the lake. You see, the vast majority of our wind/weather comes from the west/southwest. So, if you put in at North Toledo Bend State Park for example (which I can testify has a very good launch), and you sailed the lake all the way to South Toledo Bend State Park (another great launch), you'd be sailing on a beam reach or possibly just a tiny bit of a close reach for the vast majority of the lake. You could then, if you wanted, go back of the lake on the opposite reach and in places a bit of a run. All in all, it should be predictably good sailing - depending on a few things.
In the summer, say from the middle of June to around the last part of August, conditions are pretty calm. Winds light and variable, as they say. If I were going to make that cruise (and that's just what I'm planning, in a year or two), I would plan to do it, if possible, in late April or early May. If not then, I'd wait until late August or early September. During those seasons, it seems there is always a gentle west wind on the lake, and sometimes it even gets pretty brisk. (To quantify, I'd say usually 5-8 knots, sometimes 10-12 knots.)
And, if you come in those times, you avoid that unbearable heat/ humidity that I'm sure you are all too familiar with in Texas.
Moving on, there is one other thing concerning the weather that I'd like to talk about. Toledo Bend has something of a sinister reputation because heavy weather seems to come from out of nowhere with no advance warning. When I say heavy, of course it varies, but I have pictures of three to five foot swells that turn into six foot breaking waves in the lee coves. Those are the largest seas I've ever seen, and I know that makes me a novice in regards to weather, but I feel pretty comfortable saying that I wouldn't want to be on those waters in a 20 foot sailboat.
So, to make a long story short concerning the weather, if you don't have on-board weather detection systems, I'd keep a close eye on the forecast before I went to Toledo Bend and a closer eye on the sky once I got there.
One other caution (or thing to be aware of at least) is that LA Hwy 6 crosses into Texas halfway down the lake. This of course requires a bridge. The bridge rises up to a pretty good height over the old river channel, but I'm not sure what that exact height is. I had planned on finding out before getting my own sailboat and trying this trip. A helpful resource would probably be the Sabine River Authority, who manages (for lack of a better word) the lake.
The plus side of the idea of a Toledo Bend cruise is that I think it would be a very nice one. 1,220 miles of shoreline with clearly marked boat lanes in case you just want to make some good time down the lake and *lots* of coves to explore if you have a dinghy or if your boat has a shallow draft. Plenty of chances to see wildlife from alligators to bald eagles. And if you come in the fall, the foliage should be beautiful.
If you should by chance read this, and if you do decide to come to Toledo Bend, PM me here, or email me if you can get that from my profile (I don't know, just made an account to reply to your post) and I'll be glad to offer any assistance that I can. I don't yet have a sailboat, but I have the passion, and would go to pretty great lengths to help a sailor.