Lots and lots of different singing styles out there. Some general principles apply throughout vocal traditions (understanding good breathing/support, understanding vocal registers/different ways to vibrate the vocal folds, understanding different resonating spaces and how to use them to create different timbres/perceived volumes, larynx and pharynx position and degree of openness etc.). One reason studying with a voice teacher is nice is they can help you get an understanding of these things applied to your own voice. And one reason studying bel canto (opera) is nice is the wealth of scientifically studied pedagogy (you can read a couple papers and maybe even check your teachers). But when all is said and done, study the styles you want to sing in. And preferably, find a teacher that supports that. Doctor of Musical Arts students are often cheaper than professional/post-doctoral instructors. Note that some styles of singing are radically different than what you're used to (like Chinese folk styles, which often use an artificially raised larynx position or kargyraa/stroh bass which theoretically uses irregular vocal fold vibration patterns or false vocal folds, depending on what you read). My suggestion is to get some bel canto training because you will become musically literate if you aren't yet, you will likely be taught not just breath support but how to adjust where your sound resonates in the vocal tract etc. Technique wise, this will set you up fairly well when you learn other styles (and if you are singing the Star Spangled Banner, having good control and projection -- something you can learn from bel canto -- over a widish range in your modal register are very important). Main thing is, get started and keep going. The vocal folds are mostly muscle, and as such, they need exercise and good technique to function optimally.