It's somewhat challenging to figure out what to voice (that's the word for drawing attention to something). As you say, in some chords certain notes might be voiced louder than others. Oftentimes it's just the upstemmed notes or the highest notes, but sometimes you want to change things up in highly repetitive passages.
How to do that? Lots of practice with balancing and touch. You can try playing forte legato on your melody and piano staccato on your accompaniment.
At the end of the day I think you're overthinking the specifics. You need to trust your ears and let yourself do what comes naturally. The flow of the music and tailoring to its needs is more important than any specific rules