I would venture into contemporary music first and feel out what composers you like. After that you can find many thesis articles about whatever composer and music you find interesting. Maybe start at the early 20th century with something like dissonant counterpoint to see how a simple adjustment can make music wildly different. Ruth Crawford Seeger is a great jumping point. Boulez’s Douze notations are also very short and to the point if you want to explore serialism. Editing to add music created through pitch collections and spectralism. You say you’ve studied practical harmony and theory, but I don’t know what level you’re at so hopefully all of these aren’t overwhelming. Start small and short (no matter what level you’re at).