I had a sock out and evenend anchored once or twice saw lots of fish suspended at 30 feet and 50 feet of water. I was using 3/4 oz jig and also small slabs. I was drifting 1 mph. How can I tell when my lure was at 30 ft. My line was not down but at a 45 deg angle. maybe I need a heavier jig and a different color.
You can drift if you want to. I like to put the nose of the boat into the wind and use the trolling motor to maintain a speed I choose. The key is keeping your lines as vertical as possible. The more sway you have in your lines the more ineffective you will be at targeting suspended fish with a deadstick. Also the sway makes it more difficult to feel the bites. I would say if the wind is over 10MPH use the heaviest head moes makes. I think it's 1.5/1.7 oz. this will help you keep your line more vertical.
As far as "guesstimating" how far down you are there are a couple tricks several guys use. 1. Learn your equipment. My particular reels bring up about 28-30" of line per handle turn. So if I need to come up 10ft lets say I'm going to turn the handle about 4 times. And then let the fish tell me to do from there. The second trick that can help you with those suspended fish is running 2 lures about 18-24" apart. This way if your bottom lure is below the fish and your top lure is catching fish you can make the needed depth adjustments. Also running tandem lures I will often run 2 different colors or sizes to help me decide what the fish prefer that particular day.
I hope this all helps. This has been a different winter time fishing year. I've seen hot swimbait bites and then hot deadstick bites. Pay attention to the water temp on any given day and let the fish tell you what to do!!