First off, it's important to note that these are 3 different things. They allow you to accomplish 3 different goals and should be addressed as individual options.
Supersets are great. I use them to get a ton of work done very quickly. Usually when I do back I'm also doing at least shoulders or chest, and sometimes all 3. I always superset my back work with chest or shoulder movements. It's the perfect way to 1. shorten your workout, 2. keep your heart rate up and 3. go heavy because the muscle itself will get plenty of rest while you hit the other movement. If I was trying to build strength in a certain movement, aka powerlifting, then that would be a different thing because going back and forth does limit somewhat how heavy you can go because your heart rate should be elevated, and you're CNS usually won't like switching back and forth while also going heavy.
Drop sets are about exhausting the muscle. Your body doesn't like using all of the fibers in a muscle if it doesn't have to. It only recruits the muscle fibers it needs to get the job done. That's why people use heavy partials in powerlifting. It "teaches" the CNS to recruit as many muscle fibers as possible. Even when you lift heavy, there are still muscle fibers which are not used. When you do a drop set, the idea is that as the primary muscle fibers weaken your body will have to recruit the as-yet unused fibers, promoting the most trama and therefore the most growth potential. This is similiar to training to failure in that some find they respond well to it while others find they don't. Usually the body can only handle one drop set at the end of the session for the muscle, so this technique doesn't offer the same cardiovacular and fat-burning benefits you'll get with supersets.
I'm personally not a fan of pre-exhaustion techniques. The idea is to focus more closely on one muscle by making it tired from an isolation movement before moving on to a compound movement. I've found that there are so many variations of each movement that it's easy to adapt things to focus on certain muscles, if that's your goal. Personally, I just prefer to find the variations that I like best and go with those.
There are a number of alernatives to pre-exhaustion that I prefer. Next time you do a pressing movement, while you do the first 5-8 reps try to squeeze your hands towards eachother. This works extremely well with bench press and overhead press. After you do the reps while you are squeezing your hands together, stop squeezing and just rep out as many as you can. The squeezing takes your arms out of the movement somewhat and helps you nail the bigger muscles, then repping out lets you finish it off. This method is also good at teaching you to recruit specific muscles as you lift. If you find that you're arms tire out before the bigger muscles do then this is a good method to try now and then.
Bodyweight- 231, currently cutting to under 220
Raw total- 1280
Geared total- 1490
Best gym lifts, single ply-
Only goal- ELITE as soon as humanly (and chemically) possible.