The best way to learn the techniques you wanna learn would be to listen to the songs you think of as the best trap songs you know of and dissect them. Write down how their song is arranged, what instruments are in which sections, what each instrument is doing - the rhythm, the melodic content if it changes pitch, what FX are going on in the background and when, how loud the different elements are.

Go look up the Ill Gates Methodology video on youtube (i've probably linked it in this forum a half dozen or so times), and follow his instructions on how to analyze songs. If you can follow the homework assignment he gives you in the middle/end of the video, you'll probably know more about trap than any youtube tutorial or forum post could tell you.

Here are some good tips to get you started in the right direction, though:

• You're on the right track with the tempo: 100 BPM and 200 BPM are identical, depending upon how you are writing the beat. A 1 bar 100 BPM loop where you alternate between the kick on the 1 & 3 and the snare on the 2 & 4 will sound indistinguishable from a 2 bar 200 BPM loop where you alternate between the kick on the 1 and the snare on the 3. You can leverage this to your advantage by writing a song in half-time at something like 150 BPM, then for the second drop you can "double time" your drop and give it that much more energy while never changing the tempo.
• If you have trouble thinking of an arrangement when you have a 4, 8, or 16 bar loop (or whatever), duplicate it out to be however long you think the song should be (3-4 minutes is a good range for trap but in no way is a hard line), and start putting down arrangement markers for the different sections. Then just delete any clips that should not be in those sections. So your intro might not have your drop lead or any sub bass, but it probably will contain some of the melodic content you've thought up and maybe some percussion. Your breakdown obviously isn't gonna have most or all of your percussion, so you can just remove it from there. As you clear away the unnecessary clips, even though you haven't changed anything a fully completed song is already beginning to form. Just start consolidating clips and making changes as necessary.
• You can either have a complicated sound or a complicated melody, not both. As you study the songs you like, you'll start to notice how the notes move - falling over and octave or rising over an octave, jumping between the tonic and the octave, or staying within 2 or 4 semitones. A simple melody is not a bad one, and if you can hum or sing the melody with your mouth you're on the right track.