I'm gonna add to this.
*1 --- Be careful when you say to use compressors on everything. I used to do that way too much, and it sounded pretty bad. However, it was back when I knew nothing about compressors other than the fact that they push down loudness (like a year ago, before the month that I considered my "turning point"). When you use compressors, remember to do a strict before-and-after comparison. Either you have an A/B function in your compressor, or you can switch the compressor on/off and compare like that. If it truly sounds better to you, then of course keep it. If it doesn't sound quite right and you don't know why, try looking for examples of what you were aiming to accomplish.
*2 --- I do this notching/boosting with my kicks/basses, and I personally think it's a great idea. Also, signal chains will certainly make a difference in how things sound, depending on the elements in the chain. For example, compression after reverb is different from reverb after compression. Generally speaking, reverb after compression sounds more natural. If you compress a reverbed sound, it'll be more obvious since the reverb tail will be affected too. On the other hand, if you reverb a compressed sound, it'll simply sound nice and big, depending on the tones you use for the instrument or reverb.
*3 --- Absolutely. Drops like those are such fun to do. Two examples:
My Metroid ReMix with AngelCityOutlaw (1:22)
(2:04)