There is one, maybe two spots I know of that holds fish that you could easily fish with 200' of cable. Mack Bar and Minneapolis Beach. Maybe Sunnybank, but they usually seem to be a little deeper there

The rest you're going to want 300 feet, minimum, when you take into account the blow-back. I have 600 feet on mine now, and am glad of it when fishing the deep water above the yacht club in January.
Use 12's, maybe even 15# balls to keep your lines down straighter to maximize your depth. If you're not bouncing bottom every minute or two, you're not fishing deep enough.
The other thing is to run and gun them. Look for a pile of them together on the finder and send down a dropshot rig or jig. No riggers needed, and while it isn't as productive most days, it sure is more fun.
If trolling, glow flatfish and ace hi-flies work great. I've gotten some good tips on other baits from other guys on here, too, but I'll let them chime in with those. Whatever you're pulling, ground speed between 1.0 and 1.5 mph seems to be the best place to start. Vary speed every once in a while to give the fish a different look.
As for guides, Joe Heinlen with Lake Chelan Adventures is a good choice as well. If you're on the water and see either of these guys, just ask them what they're hitting on that day and they will straight-up tell you. When I was getting started on this fishery, they were very helpful - especially once they got to see my boat every once in a while on the water. I ended up taking a guided trip a couple of years ago to put the final 20% of the puzzle together. Wish I would have done that years earlier - I could have caught hundreds more fish in the same amount of time.
This is just free advice, so take it for what it's worth.