For example In the chorus of the song say I have a pluck sound from a synth, do I write a chord progression or melody?
That's entirely up to you.
Keep in mind that if you'd like to get the best of both worlds you can use both. Chord progressions can contain melodies like in this track.
Obviously chords contain more notes so they sound bigger but you can always (in massive) just bump up the number of voices per not to make melodies sound bigger
Sure. It doesn't matter how many notes are playing. The way you get "bigger" sounds is by emphasizing the correct frequencies. Making sure that the bass and the mid's are properly being represented.
Also what sounds should I use chords or melodies for?
This is also entirely up to you.
You should use the sound that best represents the chords or melody. With real instruments it's lot more obvious because of the natural limitations of the instruments. Playing fast tremolos on a single note for example isn't best suited for a piano. With electronic music you don't really deal with those limitations though.
? Is there any sounds I shouldn't write chords with and any sounds I shouldn't write melodies with?
I'd avoid writing chords in the very low bass frequencies because you lose a lot of note clarity in that range. Muddiness will begin to take over.
